The Effect of Growth Interruption on Structural and Optical Properties of InAsP/InP Multiple Quantum Wells
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C. A. TRAN, J. T. GRAHAM, R. A. MASUT * and J. L. BREBNER Groupe de Recherche en Physique et Technologie des Couches Minces, Universit6 de Montreal, D6partement de Physique, C.P. 6128, Succ. "Centre-ville". Montreal, Qu6bec, CANADA, H3C 3J7. "*Ecole Polytechnique de Montreal, D6partement de G6nie Physique, C.P. 6079, Succ." Centreville", Montr6al, Quebec, CANADA, H3C 3A7. ABSTRACT A systematic study of the effect of growth interruption on the interface roughness of InAs•P 1_./InP heterostructures has been carried out. High resolution X-ray diffraction, photoluminescence and optical absorption measurements for InAsP/InP strained multiple quantum wells reveal that the InAsP/InP interface is very sensitive to growth interruption. For nonoptimal growth interruption procedures a large density of interface states is created, probably as a consequence of compositional modifications within the interface region. We find that photoluminescence on its own is insufficient to characterize the interface roughness in our samples, since even for narrow low-temperature peak emissions corresponding to the multiple quantum wells, the absorption spectrum may reveal a significant density of interface states. INTRODUCTION The physical properties of semiconductors in strained multiple quantum well (SMQW) structures have attracted considerable attention, since the strained-layer structures display new electronic and optical properties not seen in the unstrained constituent materials [1]. Recent theoretical work has predicted that the optimal valence band structure for longwavelength strained quantum well lasers is found in the InAs/InP system [21 and InAsP alloys are one of the materials of choice for short-channel, high-speed devices. Furthermore, this SMQW system can be used to make an optical modulator, as has previously been demonstrated [3]. In metalorganic vapor phase epitaxy (MOVPE) growth interruption has been used largely in order to improve the interface quality of strained [41 and unstrained heterostructures [5]. The narrow width of the photoluminescence (PL) emission is offen used as an indication of high interface quality [5]. In this work we show that PL measurements on their own provide an incomplete picture of the interface roughness in strained heterostructures such as InAsP/InP, meaning that additional structural and optical techniques such as high-resolution X-ray diffraction (HRXRD) and optical absorption are needed before conclusions can be drawn about the effect of growth interruption on interface quality. EXPERIMENTS Growth of InAsP/InP SMQWs was carried out using a horizontal cold-wall quartz reactor with a graphite susceptor. The growth apparatus is equipped with a fast-switching run-vent gas manifold at the reactor inlet, and all the valves are computer controlled. The 115 Mat. Res. Soc. Symp. Proc. Vol. 326. @1994 Materials Research Society
substrates used were InP(001) and InP(001) 20 off towards [100], both doped with Fe. Tertiarylbutylarsine (TBAs), trimethylindium (TMIn) and pure phosphine (PH 3 ) were use
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