Improvement in performance of high-operating temperature HgCdTe photodiodes

Abstract

One of the key factors determining HgCdTe photodiode quality is acceptor doping efficiency. This paper presents significant progress made over the past 3 years in development of acceptor doping technology in metalorganic chemical vapour deposition (MOCVD) HgCdTe photovoltaic detectors. High acceptor doping is required for P +-contact layers, whereas low doping is necessary for p-type base absorbing layer. Previously, AsH 3 precursor was used as an acceptor dopant. This precursor is partially incorporated as electrically neutral As–H pairs, which are likely to be recombination centres in HgCdTe and in consequence they influence the carriers lifetime lowering. Substituting AsH 3 by TDMAAs resulted in higher carrier lifetimes and thereby about one order of magnitude higher R 0 A product of HgCdTe photodiodes at temperatures close to 230 K. Finally, it is shown that the response time of HgCdTe photodiodes at weak reverse bias condition is mainly limited by the drift time of carriers moving into p–N + junction. Using the reverse bias higher than 50 mV, the transit time across the absorber region limits the response time. The response time of small-area devices decreases in the region of weak reverse bias achieving value below 1 ns.