A Photoluminescence Investigation of Ion Beam and Electron Cyclotron Resonance ETCH-Induced Damage on GaAs/AlGaAs Multi Quantum Well Structures

ABSTRACTThe presence of highly energetic ionic and neutral species during dry etching generates damage in device structures which significantly reduces their performance. In this study we have utilized photoluminescence spectroscopy (PL) on GaAs/AlGaAs Multi Quantum Well (MQW) structures to assess and compare the relative damage induced by the standard ion beam etch technique and the “less damaging” newer Electron Cyclotron Resonance (ECR) etch technique. MQW structures with well widths of 2.7, 6.4, 10.8, and 81 nanometers (nm) at a distance from the sample surface of 40.5, 83, 130, and 170 nm respectively were grown by molecular beam epitaxy. In order to minimize the effect of the radically different chemistries present in reactive ion etching and in ECR reactive etching we have chosen to initially compare the damage-induced luminescence degradation resulting from Ar irradiation only. The PL intensity is shown to correlate well with the ion dose and energy. At equivalent total surface erosion under Ar irradiation the ECR process is shown to cause significantly less deterioration on QW PL yield. In the ion beam case a dose corresponding to a surface sputtering of less than 100 angstroms of the AlGaAs barrier causes total extinction of the PL from the QW lying at 1000 angstroms below the surface. By comparison under similar conditions no degradation is detected in the ECR irradiation case. Even at higher ECR doses equivalent to removal of up to 30 nm from the top AlGaAs barrier layer only minimal degradation is observed.