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Numerical analysis of a CdS/PbSe room-temperature heterojunction photovoltaic detector is discussed as to provide guidelines for practical improvement, based on the previous experimental exploration [1]. In our experiment work, the polycrystalline CdS film was prepared in hydro-chemical method on top of the single crystalline PbSe grown by molecular beam epitaxy method. The preliminary results demonstrated a 5.48×108 Jones peak detectivity at λ=4.7μm under zero-bias. However, the influence of some material and device parameters such as carrier concentration, interface recombination velocity remains uncertain. These parameters affect the built-in electric field and the carriers’ transportation properties, and consequently could have detrimental effect on the device performance of the CdS/PbSe detector. In this work, therefore, the numerical analysis is performed based on these parameters. The simulation results suggest that the device performance can be improved at least 4 times by increasing CdS concentration for two orders of magnitudes, and the device performance will degrade severely if the interface recombination speed is over 104 cm/s.

Polycrystalline lead salt photoconductive (PC) detectors have been widely used for applications in the 1-5μm spectral range because of their low cost, room temperature operation and high detectivity. However, the physical mechanism of such detectors had not been un-ambiguously understood. In order to improve the performance, we proposed a charge separation junction (CSJ) model to analyze and guide our material synthesis process, which has led to PbSe PC detectors with record high detectivity. On the other hand, the performance of photovoltaic (PV) detectors using Pb-salt epitaxial films on Si substrates has been limited by their high defect density even though the ideal performance of the PbSe PV detector was theoretically proven to be higher than the most popular HgCdTe PV detectors at near room temperature, due to its low Auger recombination property. Inspired by the high material quality of self-assembled lead salt microcrystals, we developed a novel method to produce PV detectors using PbSe micro-crystals based on our studies on the PC detector research that showed promising preliminary results.

An antireflection coating material for optically pumped group IV-VI lead-chalcogenide semiconductor light emitting devices has been proposed. The coating has been used to increase the photo-pumping efficiency. Theoretical model showed that with the proposed AR coating with a quarter wavelength thickness, 0.008% reflectivity could be achieved in the 980nm-982nm wavelength region. The antireflection property of the coated film was investigated by FTIR-spectroscopic reflectance measurement. Room temperature continuous-wave photoluminescence measurement from AR-coated multiple quantum well structures showed up to 4-times increment in the PL intensity, compared to uncoated ones.

Low dimensional lead salt structure such as quantum-well (QW) structure is proposed for the fabrication of opto-electronic devices. Among [100], [111], and [110] orientations, [110]-orientated QW structure offers the highest gain. Theoretical simulations of [110] QW Pb-salt edge-emitting lasers show a 70-degree temperature increase in continuous-wave (CW) operation compared to the conventional [100]-orientated lasers. With modestly reduced Auger recombination of low dimensional material and with improved heat dissipation for laser structure, CW operation with about 10 mW output powers at room temperature for PbSe QW laser is predicted. PbSe epitaxial layer and PbSe/PbSrSe QW structures were, for the first time, successfully grown on [110]-orientated BaF2 substrate by molecular-beam-epitaxy (MBE). The linewidth of the rocking curve from high-resolution x-ray diffraction (HRXRD) measurement for PbSe thin film is 60 arcsec, which indicates high crystalline quality. The dislocation density estimated by the rocking curve is 1.18x107 cm-2. Photoluminescence intensity of [110]-orientated samples was twice as high as that on [111]-orientated BaF2 substrates from the same MBE run.