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

Abstract

Strain effects and atomic arrangements of 60° and 90° dislocations near the ZnTe/GaAs heterointerface Appl.Local interface composition and extended defect density in ZnSe/GaAs(001) and ZnSe/In 0.04 Ga 0.96 As (001) heterojunctions J.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 Ga 2 Se 3 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 Ϫ2 . 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 ͑DH͒ 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 Ϫ2 was obtained when the As-terminated GaAs surface was Zn treated. The Zn treatment prevented the formation of the Ga 2 Se 3 layers. When we alternated the exposure between Zn and As fluxes, excess ZnAs x 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 ZnAs x compounds, and the density of dark defects fell to 2ϫ10 4 cm Ϫ2 .

Photoemission study of the solid-state interdiffusion in hybrid Fe/ZnSe/GaAs(001) heterostructures

“…29 For temperatures raising from 250 to 450°C, the formation of Ga 2 Se 3 -like stoichiometry layers has been reported; except in the case where Zn-controlled passivation of the GaAs surface is made when ZnAs x compounds are formed. 30 Curiously enough, no equivalent photoemission study of the thermal stability of very thin ZnSe epilayers on GaAs has been published. We have only found the experimental study reported by Chen et al 26 for 5000-Å-thick ZnSe.…”

X-ray reflectivity from ZnSe/GaAs heterostructures

“…In recent years, many works have reported the formation of a Ga 2 Se 3 -type compound within the ZnSe/GaAs interface under specific growing conditions. 3,8,15,16 However, other investigators did not observe this phenomenon. 5,10,11 A study of the reconstruction process during the growth of crystalline Ga 2 Se 3 on GaAs substrates 17 proved the stability of this compound.…”

“…Another possible candidate for the transition layer is a Zn-As-type composition. 8,9 Despite the reported energetic instability of these compounds, 3 the presence of a thin ZnAs intermediate layer was detected in ZnSe/ GaAs epilayers 8,18 by a TEM method. Both models are dis-a͒ Present address: RIGAKU Corp., 3-9-12 Matsubara-cho, Akishima-shi, Tokyo 196, Japan.…”

“…1,2 The wide band-gap energy and blue-green spectral operation region of these devices has led to considerable interest in the structure 3-7 and growing technology [8][9][10] of ZnSe/GaAs heterojunctions. Epitaxial ZnSe layers grown on GaAs substrates by molecular beam epitaxy ͑MBE͒ or metalorganic vapor phase epitaxy ͑MOVPE͒ technologies demonstrate excellent electronic properties compared to other II-VI materials.…”

“…In many cases, the interface imperfections are responsible for subsequent device problems, e.g., shortening of operation time and decreasing of radiated intensity. The structure and composition of the interface and the bulk structure of ZnSe/GaAs have been studied by a number of physical and chemical methods, e.g., high-resolution x-ray diffraction ͑HRXRD͒, 10 photoluminescence ͑PL͒, 7,10,11 reflection high energy electron diffraction ͑RHEED͒, 4,8,9 transmission electron microscopy ͑TEM͒, 12,13 scanning tunneling microscopy ͑STM͒, 14 and extended x-ray absorption fine structure ͑EXAFS͒. 15 Our research effort aims to investigate the bulk structure of ZnSe films grown by MBE on ͓001͔ GaAs substrates and the ZnSe/GaAs interface by means of x-ray reflectivity.…”