Development of position sensitive semiconductor photo-detector

我们一直在研究光子探测器的可能性，它可以测量光子的入射位置，精度远远好于1 mm。由于探测器的投影灵敏度低至单光子能级，现有的技术，如电荷耦合器件，不适合目前的应用。探测器需要具有一定的内部放大机制，以获得不同于CCD器件的更好的信噪比。在本研究中，我们致力于开发具有内部放大机制的光敏半导体器件，其实现方式为：1)雪崩放大或2)在探测器元件表面形成内置晶体管。我们尝试制作间距为100微米的雪崩光电二极管的线性阵列，以获得位置灵敏度。在第二种方法(2)中，我们应用了一种MOS像素器件，其输出信号将通过形成在每个像素表面的PMOS晶体管来放大。我们已经研究了几种测试结构，并观察到了光子激发的放大信号，由于本研究的资源和时间有限，我们还没有成功地制作出满足最初目标要求的样品。然而，在本研究中考察的两种方法被发现是非常有希望的。

We have been investigating the possibility of the photon detector which can measure the incident position of photon with an accuracy far better than 1 mm. Since the projected sensitivity of the detector is as low as a single photon level, the established techniques such as CCD are not suitable for the present application. The detector should have some internal amplification mechanism to achieve a better signal to noise ratio unlike a CCD device.In the present study, we have made a effort to develop photo-sensitive semiconductor device with an internal amplification mechanism which would be realized by 1)an avalanche amplification or 2)an built-in transistor formed on the surface of the detector elements.Along the first approach(1), many studies had been made in the past decade to develop an Avalanche Photo Diode (APD). We have tried to make a linear array of the APD with its pitch of 100 um to acquire a position sensitivity. A successful operation was observed with internal gain of 20 in a single cell device and investigation on the multi-cell linear array structure is now in progress.In the second approach(2), we applied a MOS pixel device whose output signal would be amplified by the pMOS transistor formed on the surface of each pixel. Several test structure have been investigated and have observed the amplified signal initiated by photons.Due to the limited resources and time of the present study, we have not yet succeeded to fabricate the sample which satisfies the requirements aimed at first. However, the two approaches examined in the present study was found to be very promising.