JPH01138486A - Multichannel type semiconductor radiation detector - Google Patents

Abstract

PURPOSE:To improve the spatial resolution of a sensor by providing earth electrodes between charge collecting electrodes. CONSTITUTION:The earth electrodes 4 are provided between the charge collecting electrodes 2 on one surface of Si crystal 1, and a surface barrier electrode 3, is formed on the other surface. Consequently, lines of electric force in the detector become straight and charges generated by semiconductor crystal between electrodes are gathered to the earth electrode. Therefore, charges gathered by channels are generated by radiation incident below the charge collecting electrodes, pulses having small crest values decrease, and the energy resolution of each channel is improved. Further, the separation between channels is improved and the spatial resolution of the sensor is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to semiconductor radiation detectors used in radiation dosimeters, medical radiation diagnostic equipment, industrial X-ray nondestructive testing equipment, and the like.

Conventional technology In general, semiconductor radiation detectors include those composed of elemental semiconductors such as Si and Ge, as well as those composed of elemental semiconductors such as CdTe and GaAs.
, CdSe, 11g12, and other compound semiconductors. Among these, CdT'e has a wide forbidden band width of about L5 eV at room temperature, allowing operation at room temperature, and has high radiation absorption, so high sensitivity can be obtained.

Semiconductor radiation detectors include full-depletion layer detectors, in which ohmic junction electrodes are formed on opposing surfaces of a high-resistance crystal with a low carrier concentration, and the entire crystal is a radiation-sensitive layer, as well as full depletion layer detectors, in which a surface barrier type electrode is formed on one surface. , a surface barrier type detector that forms an ohmic junction electrode on the other side and detects radiation in a depletion layer generated near the barrier, and a pn junction that forms a pn junction on one side and an ohmic junction electrode on the other side and reverse biases the pn junction. ρn detects radiation in a depletion layer generated by applying a voltage
There is a junction type detector. Furthermore, there is a blocking type semiconductor radiation detector in which a blocking layer made of an insulator or the like is formed on one surface of a semiconductor crystal, a metal electrode is laminated thereon, and an ohmic electrode is provided on the opposing surface. The ohmic electrode of a semiconductor detector made of these structures collects charges generated in a sensitive layer within the semiconductor. There is also a structure in which a blocking layer and a metal electrode are laminated on both sides of a semiconductor crystal, but in this case, one electrode becomes a charge collection electrode due to charge tunneling.

In any multi-channel semiconductor radiation detector, a plurality of charge collecting electrodes are arranged at a specific pitch.

Problems to be Solved by the Invention In order to operate a multi-channel semiconductor radiation detector,
In either method, a DC voltage is applied between opposing electrodes. This generates an electric field between the electrodes. At this time, the fifth
As shown in the figure, the lines of electric force 12 in the multi-channel semiconductor radiation detector 18 are not straight lines because one electrode is divided into multiple pieces, and the lines of electric force between the electrodes are also deep and the charge collecting electrode focus on. Therefore, charges generated in the semiconductor crystal 9 between the electrodes are also collected. This charge appears as a pulse with a low wave height as shown in the radiation characteristic diagram of FIG. 6, and the half width of the photoelectric peak becomes large, which also affects the energy resolution of the detector. Furthermore, separation between channels becomes poor, resulting in low spatial resolution when used as a line sensor.

Means for Solving the Problems A multi-channel semiconductor radiation detector has a structure in which a radiation detection semiconductor is sandwiched between electrodes, and at least one of the electrodes constitutes a charge collecting electrode divided into many parts. A ground electrode is provided between the charge collection electrodes.

By providing a ground electrode between the active charge collecting electrodes, the electric lines of force within the detector become straight lines, and the charges generated in the semiconductor crystal between the electrodes are collected on the ground electrode.

Therefore, the charge collected in each channel is generated by the radiation incident under the charge collection electrode, and pulses with small peak values are reduced, increasing the energy resolution of each channel. Also, there is better separation between each channel, improving the spatial resolution of the sensor.

Example Examples of the present invention are shown below.

Example 1 FIG. 1 shows an example of the present invention. On one surface of the S1 crystal 1, a pattern of Au was deposited to form an ohmic connection between the charge collection electrode 2 and the ground electrode 4.

On the other surface, AI was deposited by vacuum evaporation to form a surface barrier electrode 3. The gap between the charge collection electrode 2 and the ground electrode 4 was 5 μrn. Charge collection electrode 2 and surface barrier electrode 3
A DC high voltage was applied during this period, and the radiation characteristics at 24' A m were measured. Figure 2 shows the measurement results.

Each channel has a 60KeV photoelectric peak of 2”Am,
It is sharper than in Figure 6, which shows the radiation characteristics of the conventional detector, and the number of pulses with low wave heights has decreased. That is, this indicates that the charge generated between the charge collection electrodes is not collected by the charge collection electrode 2.

Note that similar results were obtained when germanium was used.

Embodiment 2 FIG. 3 shows another embodiment of the present invention. The multi-channel semiconductor radiation detector shown in Figure 3 is a fully depleted layer type with a resistivity of 1.
An ohmic electrode 6 is formed on one side of the CdTe crystal 5 of 06 to 109 Ωcm by electroless plating of PT.
An ohmic contact was formed on the other surface by pattern vapor deposition of Au to form a charge collection electrode 7 and a ground electrode 8. The radiation characteristics of this multi-channel semiconductor radiation detector are shown in FIG. The 60 KeV photoelectric peak of 241 Am in each channel is sharper than that of conventional detectors, pulses with low wave heights are reduced, and spatial and energy resolution are improved.

Although there are other materials F that can be used as a radiation detector, such as Cue, CdSe, GaAs, and Hg I2, similar results were obtained.

Effects of the Invention According to the present invention, a multi-channel semiconductor radiation detector is provided which has good separation between channels and high spatial resolution, and each channel has excellent energy resolution.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are a plan view and a cross-sectional view showing the configuration of a multi-channel semiconductor radiation detector according to a first embodiment of the present invention, respectively, and FIG. 2 is a first embodiment of the present invention. The radiation characteristic diagrams of the multi-channel semiconductor radiation detector in the example, FIGS. 4 is a radiation characteristic diagram of a multi-channel semiconductor radiation detector according to the second embodiment of the present invention, and FIG. 5 is a schematic cross-sectional diagram showing lines of electric force of a conventional multi-channel semiconductor radiation detector. , FIG. 6 is a radiation characteristic diagram of a conventional multi-channel semiconductor radiation detector, and FIG. 7 is a schematic cross-sectional view showing lines of electric force of the multi-channel semiconductor radiation detector of the present invention. 1... S1 crystal, 2... Charge collection electrode, 3... Surface barrier electrode, 4... Ground electrode. Name of agent Patent attorney Toshio Nakao 1 person Figure 1 3 Surface R wall voltage Figure 2 Figure 4 Pulse liquid height 5

Claims (2)

[Claims] (1) It has a structure in which a semiconductor for radiation detection is sandwiched between electrodes,
A multi-channel semiconductor radiation detector in which at least one of the electrodes constitutes a charge collection electrode divided into many parts, the multi-channel semiconductor radiation detector having a ground electrode between the charge collection electrodes. . (2) A multi-channel semiconductor radiation detection device according to claim 1, characterized in that the semiconductor is one using cadmium telluride, cadmium selenide, gallium arsenide, mercury iodide, silicon, or germanium. vessel.