Mid-wavelength infrared nBn photodetectors based on bulk InAsxSb1-x absorbers with a greater than 5 μm cutoff grown on GaSb substrates are demonstrated. The extended cutoff was achieved by increasing the lattice constant of the substrate from 6.09 to 6.13 Å using a 1.5 μm thick AlSb buffer layer to enable the growth of bulk InAs0.81Sb0.19 absorber material. Transitioning the lattice to 6.13 Å also enables the use of a simple binary AlSb layer as a unipolar barrier to block majority carrier electrons and reduce dark current noise. Individual test devices with 4 μm thick absorbers displayed 150 K dark current density, cutoff wavelength, and quantum efficiency of 3 × 10−5 A/cm2, 5.31 μm, and 44% at 3.4 μm, respectively. The instantaneous dark current activation energy at a given bias and temperature is determined via Arrhenius analysis from the Dark current vs. temperature and bias data, and a discussion of valence band alignment between the InAsxSb1-x absorber and AlSb barrier layers is presented.

No abstract

The first detailed comparison has been made of the metalorganic vapor phase epitaxy growth rates of CdTe, ZnTe, and ZnSe, measured in situ with laser reflectometry. The comparison also includes the photo-assisted growth with visible radiation from an argon ion laser. Using a standard Group II precursor (DMCd or DMZn.TEN) partial pressure of 1.5 x 104 atm, VI/II ratio of I and DIPM (M = Te, Se) the maximum growth rates are in the region of 10 to 15 AU/ s. Decrease in growth rates of ZnTe at higher temperatures or higher laser powers have been attributed to the desorption from the substrate of unreacted Te precursor. The behavior of DTBSe is quite different from DIPSe for both pyrolytic and photo-assisted growth. The maximum growth rate is around 1 AU/ s with very little photo-enhancement, except at 300~ Secondary ion mass spectroscopy analysis of hydrogen concentration in the ZnSe layers shows high concentrations, up to 5.9 x 1019 atoms cm 3 for DTBSe grown ZnSe under pyrolytic conditions. These results show that the growth kinetics play an important part in the incorporation of hydrogen and passivation of acceptor doped material.