A unipolar, barrier-integrated HgCdTe nBn photodetector with all n-type doping and a type-I band lineup is experimentally demonstrated. Planar mid-wave infrared (MWIR) nBn devices exhibit current-voltage (I-V) characteristics that are consistent with band inversion in reverse bias, indicating a barrier-influenced behavior. Dark current saturation is observed beyond a reverse bias of approximately −0.8 V. Bias-dependent photoresponse is observed in the mid-wave infrared with a cut-off wavelength around 5.7 μm. Numerical modeling based on experimental results predicts an internal peak quantum efficiency of approximately 66%.

An n-type mercury cadmium telluride (HgCdTe) unipolar nBn infrared detector structure is proposed as a means of achieving performance limited by intrinsic thermal carrier generation without requirements for p-type doping. Numerical modeling was utilized to calculate the current-voltage and optical response characteristics and detectivity values for HgCdTe nBn and p-n junction devices with a cut-off wavelength of 12 lm for temperatures between 50 K and 300 K. Calculations demonstrate similar dark current density, responsivity, and detectivity values within 10% for the long-wavelength infrared (LWIR) nBn detector compared with the p-n junction structure for temperatures from 50 K to 95 K. These results show that the HgCdTe nBn device may be a promising alternative for achieving high performance using a simplified device structure while circumventing issues related to p-type doping in current p-n junction technology such as achieving low, controllable doping concentrations, and serving as a basis for next-generation device structures.

No abstract

GaSb nanowires were synthesized on c-plane sapphire substrates by gold-mediated vapor-liquid-solid (VLS) growth using a metalorganic chemical vapor deposition process. A narrow process window for GaSb nanowire growth was identified. Chemical analysis revealed variations in the catalyst composition which were explained in terms of the Au-Ga-Sb ternary phase diagram and suggest that the VLS growth mechanism was responsible for the nanowire growth. The nominally undoped GaSb nanowires were determined to be p-type with resistivity on the order of 0.23 X cm. The photoluminescence was found to be highly dependent on the V/III ratio, with an optimal ratio of unity.

We present in this study a theoretical and experimental investigation of the MWIR HgCdTe nBn device concept. Theoretical work has demonstrated that the HgCdTe nBn device is potentially capable of achieving performance equivalent to the ideal double layer planar heterostructure (DLPH) detector. Comparable responsivity, low current denisty ‫ܬ‬ ୢୟ୰୩ , and high detectivity ‫ܦ‬ ‫כ‬ values rival those of the DLPH device without requiring p-type doping. The theoretical results suggests that the HgCdTe nBn structure may be a promising solution for achieving a simplified MWIR device structure and addressing problems associated with reducing thermal generation in conventional p-on-n structures and processing technology limitations such as achieving low, controllable in-situ p-type doping with MBE growth techniques. Furthermore, the physical mechanisms for selective carrier conduction in the nBn structure may provide a basis to incorporate into future device structures to suppress intrinsic Auger carrier generation. Likewise, the experimental demonstration of the MWIR HgCdTe nBn devices introduces a promising potential alternative to conventional high performance p-n junction HgCdTe photodiodes. The experiments described in this study illustrate the successful implementation of a HgCdTe barrier-integrated structure. The measured current-voltage characteristics of planar-mesa and mesa HgCdTe nBn devices exhibit barrier-influenced behavior and follow temperature-dependent trends as predicted by numerical simulations. Optical measurements of the planar-mesa MWIR HgCdTe nBn device indicate a bias-dependent spectral response. Further changes to MWIR HgCdTe nBn layer structure has shown an over 10 5 A/cm 2 reduction in J dark as well as a shift to a lower turn-on operation bias. This experimental investigation highlights the potential for pursuing similar and related unipolar, type-I barrier devices for high performance infrared detector applications.