High Quality Epitaxial Growth on in-Situ Patterned Inp Substrates
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HIGH QUALITY EPITAXIAL GROWTH ON IN-SITU PATT7ERNED InP SUBSTRATES
H. TEMKIN, L. R. HARRIOTT, J. WEINER, R. A. HAMM, AND M. B. PANISH AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, NJ 07974
ABSTRACT We demonstrate a vacuum lithography process which uses a finely focused Ga ion beam to write the pattern which is then transferred to the InP pattern by low energy dry etching. Surface steps on the order of 1000-2000A in height, and lateral resolution limited only by size of the ion beam, can be efficiently prepared using moderate Ga ion fluences. The surfaces prepared by this process are damage free and suitable for epitaxial overgrowth. GaInAs/InP heterostructures grown on in-situ patterned substrates show excellent morphology and high luminescence efficiency.
INTRODUCTION Maskless techniques of pattern generation on semiconductor surfaces are of interest in the development of vacuum processing compatible with molecular beam epitaxy. The goal of this rapidly emerging field is the preparation of buried device structures in-situ, in order to perform the pattern formation and overgrowth cycles without exposing the wafer to
atmospheric and process-related contaminants [1]. Such contaminants degrade the regrowth quality and the attempts at surface cleaning often reduce or even remove the fine features formed by conventional methods. This problem is particularly acute in the preparation of quantum well based nanostructures. Finely focused ion beams, and especially Ga-ion beams, offer a powerful tool for the modification of surface properties and micromachining [2-6]. However, the use of deflected
beam techniques raises two difficult questions. First, the serial nature of the focussed beam writing necessitates long exposure times. Second, the fine focusing is obtained for beam energies of tens of KeV and substrate damage is a serious concern. We have found that the use of Ga beam writing coupled with low energy dry etching can transfer the pattern to the substrate by removal of the ion damaged layer so that it no longer poses a problem [7]. In this work we describe the use of 20 keV focussed Ga-ion beam to produce localized damage in InP substrates. The damaged regions are removed preferentially by very low energy Ar-ion beam Cl assisted etching. The combination of Ga beam writing and etching
results in surface relief of 1000-2000 A on layers of InP or InGaAs. We have combined the ion beam writing and dry etching in a common vacuum chamber with a gas source
molecular beam epitaxy (GSMBE) system. GaInAs/InP heterostructures overgrown on these in-situ prepared surface steps show excellent morphology and luminescence efficiency.
Mat. Res. Soc. Symp. Proc. Vol. 145. 01989 Materials Research Society
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EXPERIMENTAL RESULTS A schematic drawing of the apparatus and the process sequence is shown in Fig. 1. The in-situ processing section is attached to the load-lock of the gas source molecular beam epitaxy (GSMBE) chamber [8,9]. It consists of the etching and Ga-beam chambers, separated by a sample transfer sect
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