Control of the II-VI/GaAs interface reaction using hydrogen radical and Zn/As fluxes

The lifetime of II-VI-based blue-green laser diodes on GaAs substrates is limited by rapid degradation in the active layers. This degradation has been observed as dark defects in the active layer during the laser operation, where defects occurred due to stacking faults that originated from the Ga2Se3 compounds at the ZnSe/GaAs interface. The reported value of the density of stacking faults of the II-VI lasers was in the order of 10(5) cm(-2). To extend the lifetime, surface treatment of the GaAs substrate and control of the interface reaction are necessary. We investigated a new treatment technique using hydrogen-radical and Zn/As fluxes. We fabricated ZnSe-based double-hetero (DH) structures on a treated GaAs substrate and measured the density of dark defects in the light emitter area by electroluminescence microscopy. Chemical bonds at the interface were evaluated by x-ray photoelectron spectroscopy. A dark defect density of less than 10(5) cm(-2) was obtained when the As-terminated GaAs surface was Zn treated. The Zn treatment prevented the formation of the Ga2Se3 layers. When we alternated the exposure between Zn and As fluxes, excess ZnAsx interfacial layers were formed and the quality of the DH structure was unacceptable. However, hydrogen-radical exposure before and during the Zn/As treatment effectively removed the excess ZnAsx compounds, and the density of dark defects fell to 2 x 10(4) cm(-2). (C) 1997 American Institute of Physics.