Quantum-well and cavity-mode resonance effects in a vertical-cavity surface-emitting laser structure, observed by photoreflectance using hydrostatic pressure and temperature tuning

Photomodulated reflectance (PR) and conventional reflectance (R) measuremen ts as a function of hydrostatic pressure (up to 1.24 GPa) and temperature ( 150 to 310 K) were performed on an InGaAs/GaAs/AlAs vertical-cavity surface -emitting laser (VCSEL) structure. Both the cavity mode and the ground-stat e quantum well (QW) transition could be clearly observed in the PR spectra at all temperatures and pressures, whereas the corresponding R spectra reve al only the cavity mode clearly. Close to the resonance between cavity mode and QW exciton, achieved either by tuning the temperature at a fixed press ure or vice versa, an enhancement of the PR response by almost an order of magnitude was observed. The PR results have been analysed in terms of the l ineshapes of the QW exciton and cavity mode and their importance for VCSEL characterisation and fabrication has been discussed.