Development of position sensitive semiconductor photo-detector

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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.