Passivation Studies on AlGaAs Surfaces Suitable for High Power Laser Development

We report on the optical characterization of sulphur (S) passivated AlxGa1−xAs/GaAs surfaces using photoluminescence (PL) and surface photovoltage (SPV) measurements. Both techniques show an enhancement in the near bandgap signal intensity, implying a reduction of the non-radiative recombination rate at the surface. To counter the instability of S-passivation, due to re-oxidation, dielectric layers of silicon nitride were deposited using electron cyclotron resonance plasma enhanced chemical vapour deposition (ECR-PECVD); the deposition of dielectric layers up to lOOnm thick does not appear to cause significant deterioration or stress at the insulator/AlGaAs interface. The dielectric layers are shown to be resistant to oxidation, and effective in maintaining the passivation effect over a period of weeks.