Advances in composition control for 16 mm 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 RoA operability, good quantum efficiency, and low 1/f noise at 60K have been demonstrated at cutoff wavelengths to 16.3µm. The diode performance continues to improve at lower temperatures, following a diffusion-current trend to at least 35K. Measured RoA values of 2×105 ohm-cm2 for an 18 µm cutoff at 35K are the highest reported at this very long wavelength. A simple defect model applied to the area dependence of RoA at 40K implied a defect areal density of 3×104 cm−2 and a defect impedance of 3×106 ohm.