Aluminum gallium nitride/silicon carbide separate absorption and multiplication avalanche photodiodes

AlGaN/SiC separate absorption and multiplication avalanche photodiodes (SAM-APD) offer a unique approach for fabricating high gain photodetectors with tunable absorption in the deep ultraviolet regime. However, unlike conventional heterojunction SAM APDs, the formation of charge at the hetero-interface arising from spontaneous and piezoelectric polarization can dramatically affect device performance. This paper discusses the role of interface charge on device operation and the use of nitride interface control layers as a means to optimize it. A thin AlN layer inserted at the AlGaN/SiC hetero-interface is shown to be effective in reducing the net interface charge.