MIS capacitors on PbTe for 5 micron infrared detection

Metal-insulator-semiconductor (MIS) capacitors (Al/Al2O3/p-PbTe and Al/MgO/p-PbTe) on PbTe single crystals have been investigated for 5 micron infrared detection. The PbTe comes from Czochraslki single crystals, annealed to lower the carrier concentration. The insulator layers are e-beam deposited Al2O3and MgO. The C(V) curves of these MIS were checked at 77 K. The p-type semiconductor is depleted at zero bias and the flat-band voltage is from 4 to 10 volts for 1500 A° of insulator. The curves indicate a PbTe carrier concentration near 10¹⁶cm^-3, in agreement with junction characteristic measurements on the same wafers. Transient capacitance measurements on these MIS capacitors give a transient or storage time of 1 to 5 ms, with a 77 K background. Measurements of conductance and variation of conductance with frequency give a lifetime in PbTe of 0,8 to 2 ns. We conclude that such MIS capacitors can be used for IR detection in PbTe with charge-injection readout.