Thermionic emission and tunneling in InGaAs/GaAs quantum well infrared detectors

Thermionic emission and tunneling current measurements have been performed on a high In composition (x=0.3) pseudomorphic InxGa1−xAs/GaAs multiple quantum well infrared detector grown on GaAs substrate. It was found that at low temperatures (<40 K), the leakage current of the detector dominates by sequential tunneling through the ground states of quantum wells while at high temperatures (≳40 K) the data is in good agreement with the thermionic emission over the quantum well barriers. This indicates that the layers have good electrical quality, suggesting a low density of dislocations. The estimated barrier height relative to the ground state using the thermionic emission analysis of 101 meV is in good agreement with the measured cut-off energy of 98 meV of the photoresponse. The conduction band offset between In0.3Ga0.7As and GaAs is estimated to be about 200 meV.