Abstract
A systemtic study of spectral responsivity, quantum efficiency, carrier concentration, zero-bias resistance, and capacitance-voltage characteristics of LPE-grown PbTe-Pb0.8Sn0.2Te heterosturcture diodes is presented as a function of the PbTe growth temperature, 420 °C<T<650 °C. The results provide clear evidence for the migration of the p-n junction into thePbTe layer owing to interdiffusion of native defects across the interface during PbTe growth at T≳480 °C. The main effects of the junction migration on the diode characteristics are a reduction in the wuantum efficiency at wavelengths above the 6 μm and an increase in the junction zero-bias resistance. These results are interpreted on the basis of the energy-band diagrams of the heterostructure diodes obtained from the capacitance-voltage characteristics and the measured carrier concentration of the epilayers. It is shown that an energy barrier for the excited electrons in the Pb0.8Sn0.2Te layer, formed at the PbTe-Pb0.8Sn0.2Te interface, is responsible for the reduction of the photosignal above 6 μm. The junction migration is prevented by growing the PbTe layers below 480 °C. In this case, peak (∼10 μm) current responsivity in the range 1.7–2.3 A/W, quantum efficiency in the range 22–30% (both without an antireflection coating), and R0A≳1 Ω cm2 are reproducibly obtained.
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