Development of position sensitive semiconductor photo-detector

我们一直在研究光子探测器测量光子入射位置的可能性，其精度远高于1毫米。由于探测器的投影灵敏度低至单光子水平，现有的CCD等技术已不适合目前的应用。探测器应该有一些内部放大机制，以实现更好的信噪比，不像CCD设备。在本研究中，我们努力开发具有内部放大机制的光敏半导体器件，该器件将通过1)雪崩放大或2)在探测器元件表面形成内置晶体管来实现。沿着第一种方法(1)，在过去的十年中进行了许多研究，以开发雪崩光电二极管（APD）。我们已经尝试制作一个APD的线性阵列，其螺距为100微米，以获得位置灵敏度。在单单元装置中观察到内部增益为20的成功操作，目前正在对多单元线性阵列结构进行研究。在第二种方法(2)中，我们应用了一个MOS像素器件，其输出信号将被每个像素表面形成的pMOS晶体管放大。研究了几种测试结构，并观察到光子引发的放大信号。由于目前研究的资源和时间有限，我们还没有成功地制造出满足最初要求的样品。然而，在本研究中检查的两种方法被发现是非常有前途的。

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.