CN113257968B - A light emitting diode with a nitrogen polar face n-type electron blocking layer - Google Patents

Abstract

The invention discloses a light emitting diode with a nitrogen polar surface n-type electron blocking layer, which comprises a substrate, a nitrogen polar nitride layer, a polarity inversion nitride layer, and an n-type nitride ohmic contact layer in order from bottom to top , n-type nitrogen polar surface electron blocking layer, undoped superlattice structure layer, multiple quantum well active layer, p-type nitride ohmic contact layer. An n-type electrode and a p-type electrode are respectively provided on the n-type nitride ohmic contact layer and the p-type nitride ohmic contact layer. The n-type electron blocking layer with nitrogen polar face provided by the present invention can spatially limit the number of electrons entering the active region, and because the traditional p-type doped electron blocking layer is removed, it can increase the amount of electrons entering the active region. The injection rate of holes keeps the number of holes and electrons injected into the active region at a balanced level, which can improve the probability of electrons and holes in the active region radiating recombination light, thereby improving the performance of the light-emitting diode.

Description

A light-emitting diode with a nitrogen-polarized n-type electron blocking layer

technical field

The invention provides a light emitting diode (LED) with a nitrogen polar plane n-type electron blocking layer, which belongs to the technical field of semiconductor optoelectronic materials and device manufacturing.

Background technique

Because LED has the advantages of high efficiency, energy saving, high reliability and long life, and has great advantages over traditional lighting sources in terms of energy saving, emission reduction and environmental protection, it has gradually replaced traditional lighting methods such as fluorescent lamps and incandescent lamps. . However, studies have shown that, as shown in Figure 2, the internal quantum efficiency of the LED drops rapidly under the condition of high current injection, and electrons can easily overcome the limitation of quantum wells to reach the p region for non-radiative recombination with holes, which leads to high current density operation. A major factor in the decline of LED luminous efficiency under conditions has seriously restricted the application and development of LEDs. Therefore, reducing the leakage rate of electrons is one of the important ways to improve the luminous efficiency of LEDs.

Since electrons have a smaller effective mass and higher mobility than holes, and the concentration of electrons in LEDs is much greater than that of holes, the excess electrons can easily pass through the MW active region into p-type area, causing serious current leakage and reducing the luminous efficiency of the LED chip. In order to effectively block the overflow of electrons and improve the injection efficiency of holes, researchers have tried many methods to improve the structure of the electron blocking layer, including AlGaN electron blocking layers with graded Al composition, p-AlGaN/GaN superlattice electrons Blocking layer and composite polar surface electron blocking layer, etc. However, these electron blocking layers are still unable to satisfactorily solve the following technical problems: 1) The traditional p-type electron blocking layers can block electron leakage while reducing the hole injection efficiency, resulting in the radiative recombination efficiency of carriers in LEDs 2) The lattice mismatch between the active region of the multiple quantum well and the electron blocking layer is generally large, resulting in a strong polarization electric field in the active region, causing the energy band bending of the heterojunction interface, and the electron The wave function of the hole and the hole are separated in space, reducing the radiative recombination efficiency of carriers, which is the so-called quantum confinement Stark effect; 3) In order to improve the hole injection efficiency, the p-type electrons of the nitrogen polar surface are used The barrier layer often needs to be heavily doped with Mg element to induce polarity reversal, which can cause the doping aggregation of Mg in the film, resulting in the deterioration of crystal quality. Therefore, it is of great significance to further improve the design and preparation of a suitable electron blocking layer structure for improving the luminous efficiency of GaN-based LEDs.

SUMMARY OF THE INVENTION

Purpose of the invention: In view of the above prior art, an n-type electron blocking layer structure with nitrogen polar surface is proposed to improve the internal quantum efficiency of LEDs and the luminous efficiency of LED devices.

Technical solution: a light emitting diode with a nitrogen polar surface n-type electron blocking layer, comprising a substrate 101, a nitrogen polar surface nitride layer 102, a polarity inversion nitride layer 103, n type nitride ohmic contact layer 104, n-type nitrogen polar surface electron blocking layer 106, undoped superlattice structure nitride layer 107, multiple quantum well active layer 108, p-type nitride ohmic contact layer 109, and n-type nitride ohmic contact layer 109 The n-type electrode 105 provided on the ohmic contact layer 104 of the nitride type and the p-type electrode 110 provided on the ohmic contact layer 109 of the p-type nitride.

Further, the forbidden band width of the n-type nitrogen polar surface electron blocking layer 106 is greater than the forbidden band width of the barrier layer in the undoped superlattice nitride layer 107 and the barrier layer in the multiple quantum well active layer 108, And the forbidden band width of the barrier layer in the undoped superlattice nitride layer 107 is larger than the forbidden band width of the barrier layer in the multiple quantum well active layer 108 .

Further, the nitrogen polar plane n-type electron blocking layer 106 is made of AlGaN, InGaN ternary nitride material or AlInGaN quaternary nitride material with uniform or graded composition, the thickness is 1-20nm, and Si element is used for n-type doping , the electron concentration formed by doping is 1×10 ¹⁸ -5×10 ¹⁹ cm ^-3 .

Further, the number of repetition periods of the undoped superlattice nitride layer 107 is 2-20, the forbidden band width decreases linearly along the growth direction, and the length of each period is 2-10 nm, and the AlGaN/AlInGaN superlattice structure and Any of the composite superlattice structures composed of ternary or quaternary nitrides and AlGaN/AIInGaN superlattices.

Further, the nitrogen polar surface nitride layer 102 is made of gallium nitride or aluminum nitride material with uniform composition.

Further, the thickness of the polarity inversion nitride layer 103 is 0.1-1 μm, and a patterned GaN and AlN binary nitride material with uniform composition is selected.

Further, the thickness of the p-type nitride ohmic contact layer 109 is 20-500 nm, and a p-type GaN binary nitride material with uniform composition, or a p-type AlGaN, InGaN ternary nitride material, or a p-type AlInGaN quaternary material is selected. Nitride material, or AlGaN, InGaN, AlInGaN nitride material with graded composition; p-type nitride ohmic contact layer 109 is p-type doped with Mg element, and the hole concentration formed by doping is 1×10 ¹⁶ ～1× 10 ¹⁹ cm ^-3 .

Further, the number of repeated cycles of the multi-quantum well active layer 108 is 3-10, the length of each cycle is 3-15 nm, and a GaN binary nitride material with uniform composition, or an AlGaN, InGaN ternary nitride material is selected. , or AlInGaN quaternary nitride materials, or AlGaN, InGaN, and AlInGaN nitride materials with graded composition constitute the multiple quantum well active layer.

Further, the thickness of the n-type nitride ohmic contact layer 104 is 0.5-5 μm, and an AlGaN ternary nitride layer with a uniform composition, or an InAlGaN quaternary nitride layer, or a graded AlGaN and InAlGaN nitride layer is selected. Any of the AlGaN/InAlGaN superlattice structure and the composite structure composed of ternary or quaternary nitride and AlGaN/InAlGaN superlattice; the barrier layer in the n-type nitride ohmic contact layer 104 is made of Si element. n-type doping, the electron concentration formed by doping is 1×10 ¹⁷ to 1×10 ²⁰ cm ^-3 .

Beneficial effects: Compared with the traditional LED with the p-type electron blocking layer, the LED with the n-type electron blocking layer provided by the present invention has the following advantages:

1) By adopting an n-type electron blocking layer structure with a nitrogen polar face, a sufficiently high potential barrier can be provided to limit the number of electrons entering the active region, and the nitrogen polar face can provide the The electric field with the opposite direction of spontaneous polarization helps to cancel the partial polarization electric field, thus spatially limiting the concentration of electrons in the active region.

2) The direction of the spontaneous polarization electric field of the nitrogen polar surface is opposite to the polarization direction of the active region, which helps to offset the partial polarization electric field, which can reduce the quantum confinement Stark effect in the active region of the multiple quantum well and increase the number of electrons. The radiative recombination probability of holes, thereby improving the internal quantum efficiency of the LED.

3) The undoped nitride superlattice structure layer can effectively reduce the lattice mismatch between the n-type electron blocking layer and the multiple quantum well active region, thereby reducing the polarization electric field caused by the piezoelectric polarization effect , improve the effective barrier of the n-type electron blocking layer on the nitrogen polar surface, reduce the two-dimensional electron gas density at the interface of the heterojunction, and improve the spatial distribution uniformity and coincidence rate of carriers.

4) Since the p-type electron blocking layer in the traditional LED structure is removed, the injection efficiency of holes into the active region of the multi-quantum well can be significantly increased, thereby ensuring that the concentration of holes and electrons in the active region is maintained at equilibrium It is beneficial to improve the radiative recombination efficiency of electrons and holes.

Description of drawings

1 is a schematic cross-sectional structure diagram of an LED with an n-type electron blocking layer with a nitrogen polar plane provided by the present invention, wherein: a substrate 101, a nitrogen polar plane nitride layer 102, a polarity inversion nitride layer 103, n-type nitride ohmic contact layer 104, n-type electrode 105, n-type nitrogen polar surface electron blocking layer 106, undoped superlattice structure nitride layer 107, multiple quantum well active layer 108, p-type nitride ohmic layer Contact layer 109, p-type electrode 110;

2 is a schematic cross-sectional structure diagram of an LED prepared by the prior art, wherein: a substrate 201, a nitride nucleation layer 202, a nitride buffer layer 203, an n-type nitride ohmic contact layer 204, a multiple quantum well active region 205, p Type nitride electron blocking layer 206 , p-type nitride hole injection layer 207 , indium tin oxide (ITO) conductive layer 208 , n-type electrode 209 and p-type electrode 210 .

Detailed ways

The present invention will be further explained below in conjunction with the accompanying drawings.

As shown in FIG. 1 , a light emitting diode with a nitrogen polar plane n-type electron blocking layer includes a substrate 101 , a nitrogen polar plane nitride layer 102 , and a polarity inversion nitride layer which are sequentially arranged from bottom to top 103, n-type nitride ohmic contact layer 104, n-type nitrogen polar surface electron blocking layer 106, undoped superlattice structure nitride layer 107, multiple quantum well active layer 108, p-type nitride ohmic contact layer 109 , and the n-type electrode 105 provided on the n-type nitride ohmic contact layer 104 and the p-type electrode 110 provided on the p-type nitride ohmic contact layer 109 .

The nitrogen polar surface nitride layer 102 is made of gallium nitride or aluminum nitride material with uniform composition. The thickness of the polarity-reversed nitride layer 103 is 0.1-1 μm, and a patterned GaN and AlN binary nitride material with uniform composition is selected.

The thickness of the n-type nitride ohmic contact layer 104 is 0.5-5 μm, and an AlGaN ternary nitride layer with uniform composition, or an InAlGaN quaternary nitride layer, or a graded AlGaN, InAlGaN nitride layer, AlGaN/InAlGaN layer is selected. Any one of the superlattice structure and the composite structure composed of ternary or quaternary nitride and AlGaN/InAlGaN superlattice; the barrier layer in the n-type nitride ohmic contact layer 104 is n-type doped with Si element The electron concentration formed by doping is 1×10 ¹⁷ -1×10 ²⁰ cm ^-3 .

The forbidden band width of the n-type nitrogen polar surface electron blocking layer 106 is larger than the forbidden band width of the barrier layer in the undoped superlattice nitride layer 107 and the barrier layer in the multiple quantum well active layer 108, and the undoped The forbidden band width of the barrier layer in the hetero-superlattice structure nitride layer 107 is larger than the forbidden band width of the barrier layer in the multiple quantum well active layer 108 . Nitrogen polar plane n-type electron blocking layer 106 is selected from AlGaN, InGaN ternary nitride material or AlInGaN quaternary nitride material with uniform or graded composition, the thickness is 1-20nm, and Si element is used for n-type doping, doping The resulting electron concentration is 1×10 ¹⁸ to 5×10 ¹⁹ cm ⁻³ .

The number of repetition periods of the non-doped superlattice nitride layer 107 is 2-20, the forbidden band width decreases linearly along the growth direction, and the length of each period is 2-10 nm. AlGaN/AlInGaN superlattice structure and ternary Or any one of the composite superlattice structure composed of quaternary nitride and AlGaN/AIInGaN superlattice.

The number of repetition periods of the multi-quantum well active layer 108 is 3-10, the length of each period is 3-15 nm, and a GaN binary nitride material with uniform composition, or an AlGaN, InGaN ternary nitride material, or AlInGaN is selected. Quaternary nitride materials, or AlGaN, InGaN, and AlInGaN nitride materials with graded composition constitute the multiple quantum well active layer.

The thickness of the p-type nitride ohmic contact layer 109 is 20-500 nm, and a p-type GaN binary nitride material with uniform composition, or a p-type AlGaN, InGaN ternary nitride material, or a p-type AlInGaN quaternary nitride material is selected. , or AlGaN, InGaN, AlInGaN nitride materials with graded composition; the p-type nitride ohmic contact layer 109 is p-type doped with Mg element, and the hole concentration formed by doping is 1×10 ¹⁶ ～1×10 ¹⁹ cm ^-3 .

In this embodiment, the light emitting diode is composed of a c-plane sapphire substrate 101, a nitrogen polar plane GaN layer 102, a polarity inversion AlN layer 103, an n-type Al _0.2 Ga _0.8 N ohmic contact layer 104, and an n-type nitrogen polar plane Al _0.3 Ga _0.7 N electron blocking layer 106 , undoped Al _x Ga _1-x N/A _y Ga _1-y N superlattice nitride layer 107 , In _0.2 Ga _0.8 N/GaN multiple quantum well active layer 108 , a p-type GaN ohmic contact layer 109 , and an n-type electrode 105 provided on the n-type Al _0.2 Ga _0.8 N ohmic contact layer 104 and a p-type electrode 110 provided on the p-type GaN ohmic contact layer 109 .

The thickness of the nitrogen polar plane GaN layer 102 is 50 nm, the thickness of the polarity inversion AlN layer 103 is 500 nm, the thickness of the n-type Al _0.2 Ga _0.8 N ohmic contact layer 104 is 2 μm, and the thickness of the n-type nitrogen polar plane Al _0.3 Ga _0.7 The thickness of the N electron blocking layer 106 is 20 nm, the AlxGa1 _{- xN} and _{AlyGa1 -} yN layers in the undoped AlxGa1 _{- xN} / _{AlyGa1 -yN} superlattice structure 107 The thicknesses are 4nm and 6nm respectively, the length of each cycle is 10nm, repeated 20 cycles, the total thickness is 200nm, and x decreases linearly from 0.3 to 0.05 along the growth direction, y decreases linearly from 0.25 to 0 along the growth direction, In The In _0.2 Ga _0.8 N well in the _0.2 Ga _0.8 N/GaN multiple quantum well active layer 108 has a width of 3 nm, a GaN barrier thickness of 7 nm, a period length of 10 nm, repeated 20 cycles, a total thickness of 200 nm, and p-type GaN ohmic contact The thickness of layer 109 is 100 nm.

By adopting an n-type Al _0.3 Ga _0.7 N electron blocking layer structure with nitrogen polar facets, the number of electrons entering the active region is spatially and temporally limited. Specifically, the n-type nitrogen polar plane Al _0.3 Ga _0.7 N electron blocking layer can provide a sufficiently high potential barrier and an electric field opposite to the spontaneous polarization direction of the metal polar plane, so that the concentration of electrons in the active region can be controlled ; and the direction of the spontaneous polarization electric field of the nitrogen polar surface is opposite to the polarization direction in the active region, which helps to offset part of the polarization electric field, reduce the quantum confinement Stark effect in the active region of the multiple quantum well, and increase the number of electrons. The radiative recombination probability of holes, thereby improving the internal quantum efficiency of the LED. At the same time, since the p-type electron blocking layer in the traditional LED structure is removed, the injection efficiency of holes into the active region of the multiple quantum well can be significantly increased, thereby ensuring that the concentration of holes and electrons in the active region is maintained at equilibrium can improve the radiative recombination efficiency of electrons and holes. In addition, the use of the undoped nitride superlattice structure layer can effectively reduce the lattice mismatch between the n-type Al _0.3 Ga _0.7 N electron blocking layer and the In _0.2 Ga _0.8 N/GaN multiple quantum well active region, thereby It can reduce the polarization electric field caused by the piezoelectric polarization effect, improve the effective barrier of the n-type Al _0.3 Ga _0.7 N electron blocking layer on the nitrogen polar plane, reduce the two-dimensional electron gas density at the interface of the heterojunction, and improve the load-carrying capacity. The spatial distribution uniformity and coincidence rate of the carriers.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the principles of the present invention, several improvements and modifications can be made. It should be regarded as the protection scope of the present invention.

Claims (8)

1. A light emitting diode with a nitrogen polar surface n-type electron blocking layer is characterized in that: the N-type nitride-based multi-quantum-well substrate comprises a substrate (101), a nitrogen polar surface nitride layer (102), a polarity reversal nitride layer (103), an n-type nitride ohmic contact layer (104), an n-type nitrogen polar surface electron barrier layer (106), a non-doped superlattice structure nitride layer (107), a multi-quantum-well active layer (108), a p-type nitride ohmic contact layer (109) which are sequentially arranged from bottom to top, an n-type electrode (105) arranged on the n-type nitride ohmic contact layer (104) and a p-type electrode (110) arranged on the p-type nitride ohmic contact layer (109);

the forbidden band width of the n-type nitrogen polar surface electron blocking layer (106) is larger than the forbidden band width of the barrier layer in the non-doped superlattice structure nitride layer (107) and the forbidden band width of the barrier layer in the multi-quantum well active layer (108), and the forbidden band width of the barrier layer in the non-doped superlattice structure nitride layer (107) is larger than the forbidden band width of the barrier layer in the multi-quantum well active layer (108).

2. The light emitting diode with a nitrogen polar face n-type electron blocking layer as claimed in claim 1, wherein: the n-type electron blocking layer (106) with the nitrogen polar surface is made of AlGaN, InGaN ternary nitride material or AlInGaN quaternary nitride material with uniform or gradually changed components, the thickness is 1-20nm, Si is used for n-type doping, and the concentration of electrons formed by doping is 1 multiplied by 10¹⁸～5×10¹⁹cm^-3。

3. The light emitting diode with a nitrogen polar face n-type electron blocking layer as claimed in claim 1, wherein: the number of repetition cycles of the undoped superlattice nitride layer (107) is 2-20, the forbidden bandwidth is linearly decreased along the growth direction, the length of each cycle is 2-10nm, and any one of an AlGaN/AlInGaN superlattice structure and a composite superlattice structure consisting of ternary or quaternary nitride and AlGaN/AIlnGaN superlattice is selected.

4. The light-emitting diode having a nitrogen polar plane n-type electron blocking layer according to any one of claims 1 to 3, wherein: the nitrogen polar face nitride layer (102) is a gallium nitride or aluminum nitride material with uniform composition.

5. The light-emitting diode having a nitrogen polar plane n-type electron blocking layer according to any one of claims 1 to 3, wherein: the thickness of the polarity reversal nitride layer (103) is 0.1-1 μm, and a GaN and AlN binary nitride material with uniform components and subjected to patterning treatment is selected.

6. The light-emitting diode having a nitrogen polar plane n-type electron blocking layer according to any one of claims 1 to 3, wherein: the thickness of the p-type nitride ohmic contact layer (109) is 20-500 nm, and a p-type GaN binary nitride material with uniform components or p-type AlGaN and InGaN ternary nitride material is selectedThe material, or p-type AlInGaN quaternary nitride material, or AlGaN, InGaN, AlInGaN nitride material with gradually changed components; the p-type nitride ohmic contact layer (109) is p-doped with Mg element to form holes with a concentration of 1X 10¹⁶～1×10¹⁹cm^-3。

7. A light emitting diode having a nitrogen polar face n-type electron blocking layer according to any one of claims 1 to 3, wherein: the number of repetition cycles of the multiple quantum well active layer (108) is 3-10, the length of each cycle is 3-15 nm, and a GaN binary nitride material with uniform components, or an AlGaN and InGaN ternary nitride material, or an AlInGaN quaternary nitride material, or an AlGaN, InGaN and AlInGaN nitride material with gradually changed components is selected to form the multiple quantum well active layer.

8. The light-emitting diode having a nitrogen polar plane n-type electron blocking layer according to any one of claims 1 to 3, wherein: the thickness of the n-type nitride ohmic contact layer (104) is 0.5-5 mu m, and any one of an AlGaN ternary nitride layer with uniform components, an InAlGaN quaternary nitride layer, an AlGaN/InAlGaN superlattice structure with gradually changed components, an InAlGaN/InAlGaN quaternary nitride layer and a composite structure consisting of ternary or quaternary nitride and AlGaN/InAlGaN superlattice is selected; the barrier layer in the n-type nitride ohmic contact layer (104) is n-doped with Si element to form an electron concentration of 1 x 10¹⁷～1×10²⁰cm^-3。

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