MOLECULAR-BEAM EPITAXY HGCDTE INFRARED PHOTOVOLTAIC DETECTORS

We present p-on-n heterostructure HgCdTe photovoltaic device data that illustrate the high performance and flexibility in band-gap control of molecular beam epitaxy technology. This flexibility demonstration was performed by growing material for operation in the following cutoff wavelength (lambda(co)) ranges of interest: long wavelength IR (LWIR) [lambda(co)(77 K) = 9 to 11 mum], mid-long wavelength IR (MLWIR) [lambda(co)(77 K) = 6.8 mum], and very long wavelength IR (VLWIR) [lambda(co)(40 K) = 20 mum]. Detailed analyses of the current-voltage characteristics of these diodes as a function of temperature show that their dark currents are diffusion limited down to 80, 50, and 30 K for the MLWIR, LWIR, and VLWIR photodiodes, respectively. In general, the R0 A device values were uniform for the three band-gap ranges when operating under diffusion-limited conditions. We confirmed this by fabricating a 64 x 64 LWIR (lambda(co) = 10.2 mum) hybrid FPA with detectivity (D*) operability greater than 97% when operating at 77 K. The mean D* value for this device was 1.4 x 10(11) cm Hz1/2/W and it was background limited at the tested flux of 2.18 x 10(16) photons/cm2 s. This device was tested at higher temperatures of operation without changing background conditions, and it remained background limited up to 100 K.