Growth and Characterization of Extremely Abrupt InGaAs Quantum Wells
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ABSTRACT Heterostructures of InGaAs/InP and InGaAs/InGaAsP were grown by low pressure metalorganic chemical vapor deposition (LP-MOCVD) in an EMCORE GS3200 system. Highly abrupt interfaces were attained with PL line widths for the InGaAs/InP system comparable to the best values reported in the literature for any crystal growth technique, MOCVD, MBE or CBE. These structures were characterized with low temperature (10K) photoluminescence (PL), transmission electron microscopy (TEM) and high resolution X-ray diffraction (HRXD).
INTRODUCTION The production of high performance electronic and photonic devices made from compound semiconductors, such as lasers and heterojunction bipolar transistors, requires the epitaxial growth of alloy heterostructures with sharp metallurgical interfaces. It is also required that a large amount of highly uniform material be available for device fabrication. Low pressure metalorganic chemical vapor deposition (LP-MOCVD) is increasingly being used to satisfy these two requirements. In determining process capability, it is important to understand the performance of a particular LP-MOCVD reactor in obtaining smooth, abrupt hetero-interfaces. While the performance of the EMCORE reactor in growing high quality GaAs/AIGaAs heterostructures I had previously been demonstrated, system performance in growing InP based alloy hetero-structures was not well documented. It has been observed that the epitaxial growth of abrupt heterostructures of InP and InGaAs is very difficult and can serve to characterize the ability of a particular growth technique to produce high quality device structures 2 ,3, 45 . The growth of narrow quantum wells and their characterization by low temperature photoluminescence(PL) linewidth measurement is an extremely sensitive technique for determining the hetero-interface roughness in the transition between the binary and the ternary alloys 6 ,7. Since the PL peak energy is also very sensitive to the well width in thin wells, the energy shift across the wafer is an accurate measure of the thickness uniformity.
EXPERIMENTAL The EMCORE GS3200 reactor design 8 employs a load-locked stainless steel chamber that operates at low pressure, with vertical gas flow injected from a concentric ring flow flange. 209 Mat. Res. Soc. Symp. Proc. Vol. 326. @1994 Materials Research Society
Up to three 2" round wafers are held on a molybdenum platter, which is resistively heated and rotated at speeds up to 1500 rpm. The gas delivery system has provisions for pressure controlled alkyl delivery, and a pressure balanced vent/run reactant injection manifold. The samples grown in this work were of two general types: undoped Ino.53Ga0.47As quantum wells of various thicknesses with either lattice matched InGaAsP (X=1.20pm) or InP barriers, and 10 period superlattices of InGaAs/InP. All samples were grown on (100) InP substrates with Fe doping used for the multiquantum well samples and S doped wafers for the 10 period superlattices. Sources for all growths were trimethylindium, triethylgallium, 100%
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