Advances in composition control for 16 μm LPE P-on-n HgCdTe heterojunction photodiodes for remote sensing applications at 60K

With good composition control in both p-type cap and n-type base LPE layers, it is possible to make barrier-free two-layer P-on-n HgCdTe heterojunction photodiodes with very long cutoff wavelengths. Diode arrays with good R(o)A operability, good quantum efficiency, and low 1/f noise at 60K have been demonstrated at cutoff wavelengths to 16.3 mu m. The diode performance continues to improve at lower temperatures, following a diffusion-current trend to at least 35K. Measured R(o)A values of 2 x 10(5) ohm-cm(2) for an 18 mu m cutoff at 35K are the highest reported at this very long wavelength. A simple defect model applied to the area dependence of R(o)A at 40K implied a defect areal density of 3 x 10(4) cm(-2) and a defect impedance of 3 x 10(6) ohm.