Injection of point defects by oxidation of AlGaAs
- PDF / 161,960 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 56 Downloads / 200 Views
Injection of point defects by oxidation of AlGaAs
Danielle R. Chamberlin, Scott A. McHugo, Dariusz Burak, Deyon Burke, Tim Osentowski, and S. Jeffrey Rosner Agilent Technologies, Palo Alto, CA 94304
ABSTRACT Injection of point defects into GaAs/AlxGa1-xAs heterostructures by oxidation of AlxGa1-x As is investigated. The blueshift of the PL emission from GaAs quantum wells is measured as a function of rapid thermal annealing conditions in as-grown and thermally oxidized samples. Contrary to published data for point defect injection by oxidation of GaAs, oxidation of AlxGa1-xAs appears to reduce the interdiffusion of the quantum wells. The PL peak shifts after annealing have been fit assuming Al diffusion in the quantum wells and solving the singleparticle Schrödinger equation. These fits show a reduction in group-III diffusivity of over an order of magnitude with an oxidized layer of AlxGa1-xAs on the surface.
INTRODUCTION The understanding of point defect dynamics in GaAs/AlGaAs heterostructures is crucial for development and manufacturing of vertical-cavity surface emitting lasers (VCSELs) for telecommunications. Surface conditions have been known to widely affect the diffusion of point defects in GaAs for many years from studies using caps of SiO2 [1,2,3], Si3N4 [1], anodically grown GaAs [4], and thermally grown GaAs [5]. These studies have given rise to the term “impurity-free interdiffusion” corresponding to the enhancement of interdiffusion when encapsulated by SiO2 and oxidized GaAs and retardation of interdiffusion when encapsulated by Si3N4. One study has also shown the enhancement of AlGaAs/GaAs interdiffusion in a buried, oxidized AlAs layer.[6] To the authors’ knowledge, however, previously no studies of impurityfree interdiffusion have been undertaken involving the oxidation of AlGaAs, even though the wet oxidation of AlGaAs has been studied [7, 8] and is of great importance for the manufacturing of oxide-confined VCSELs. One would expect the studies of oxidized GaAs and AlAs [4,5,6] to provide an indication of the effect of oxidized AlGaAs on impurity-free intermixing. These studies have shown a dramatic increase in group-III intermixing upon anneal with when there is an oxidized layer of GaAs or AlAs present. All three of these studies [4,5,6] employed the technique of monitoring the low-temperature luminescence of GaAs/AlGaAs quantum wells and comparing the peak energy before and after annealing. This method is sensitive to small changes in the quantum well dimensions that would be undetectable by secondary-ion mass spectrometry (SIMS). Although SIMS is a more direct technique for measuring diffusion and has been employed very successfully for measuring self-diffusion in GaAs at longer anneal times [9], we have chosen to use low-temperature PL to detect interdiffusion for our experiments because it is more sensitive to the small changes present on the timescales of interest. F13.4.1 Downloaded from https://www.cambridge.org/core. YBP Library Services, on 26 Aug 2018 at 20:30:05, subject to the Cam
Data Loading...
