Room Temperature Observation of the Energy Levels of Mid-Infrared Quantum Well Lasers using Fourier Transform Infrared-Surface Photovoltage Spectroscopy

At room temperature, we demonstrate an unambiguous detection of the ground- and excited-state transitions of mid-infrared GaInSb/AlGaInSb type I quantum well (QW) lasers grown on GaAs using a new technique based on Fourier transform infrared surface photovoltage spectroscopy. It is found that none of the currently established spectroscopic techniques is able to detect even the ground state transition of these mid-infrared QW lasers at room temperature. The spectroscopic results are in reasonable agreement with the laser emission spectra at low temperatures.