Study on high gain-bandwidth product HgCdTe MWIR electron avalanche photodiodes

Abstract

HgCdTe avalanche photodiodes (APD) have been demonstrated to be one of the most promising paths for low flux and high speed applications. The bandwidth of HgCdTe e-APD has been theoretically predicted to be independent of the gain, own to its strongly dominant electron multiplication. However, when the photocurrent is high, a large number of electrons exist in the depletion region, and the electrical field in the depletion region might collapse due to the space charge effect, thus limiting the increase of the gain-bandwidth product. In this work, the structure of the device was optimized by simulation, and the effect of the light injection dose on the electric field and bandwidth of the device was studied. Finally, a mid-wavelength infrared HgCdTe e-APD device whose bandwidth hardly decreases with the increase of gain is fabricated. The response bandwidth of the APD is about 480 MHz @ gain = 625, corresponding to a gain-bandwidth product of 300 GHz.