MOCVD grown HgCdTe device structure for ambient temperature LWIR detectors

The authors report on advanced metalorganic chemical vapor deposition (MOCVD) grown HgCdTe device structure for an ambient temperature long wavelength infrared radiation (LWIR) detector application. MOCVD technology with a wide range of composition and donor/acceptor doping and without post grown annealing seems to be an excellent tool for HgCdTe heterostructure epitaxial growth structure. The N+/G/pi/G/P+/G/n(+) (where G denotes graded interface region) HgCdTe photovoltaic device concept of a specific barrier bandgap architecture integrated with Auger-suppression is a good solution for high operating temperature (HOT) infrared detectors. Selected problems of photodiode designing are indicated. Theoretical modelling using APSYS platform supports design and better understanding of the carrier transport mechanism in the photodiode structures. SIMS profiles allowed comparing projected and obtained structures and revealed diffusion processes in the structures. The negative differential resistance, clearly visible on current-voltage characteristics, evidences for Auger-suppression due to exclusion and extraction phenomena. It is shown that the thickness and arsenic doping of the active region influence the reverse bias dark current minimum and the response time of LWIR HOT HgCdTe photodiodes. Reverse bias highly (up to 50 times) increases responsivity that could reach 6 A/W at 300 K.