Surface and Interface Damage Characterization of Reactive Ion Etched MBE Regrown GaAs
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SURFACE AND INTERFACE DAMAGE CHARACTERIZATION OF REACTIVE ION ETCHED MBE REGROWN GaAs M.W. COLE*, M. DUTTA*, J. ROSSABI**, D.D. SMITH*, J.L. Lehman*** *US Army ETDL, Ft. Monmouth, N.J. 07703 **Quest Tech. Inc., Eatontown, N.J. 07724 "***JEOL USA Inc., Peabody, Mass. 01960
AND
ABSTRACT Damage resulting from reactive ion etching (RIE) and wet etching of MBE grown GaAs and the defects generated in subsequent GaAs regrowth was evaluated by Transmission Electron Microscopy (TEM), photoluminescence (PL), and Raman spectroscopy. The samples were reactively etched with HCI and C1 1 at two power densities; 0.3 W/cm2 and 0.6 W/cm2. A wet chemical (HZ0:H3PO9:HZOz) etched sample was used for comparison. The LO phonon intensities measured by room temperature Raman spectroscopy showed a strong correlation to the relative PL intensities, where the HC1 sample was found to be inferior to the others. TEM microstructural evaluation showed both HCI RIE samples to have significant interface roughness, with the sample etched at 0.6 W/cm2 showing the most structural damage in the regrowth region. Defect densities for the CIZ and wet etched samples were two orders of magnitude lower than that of the HCl etched samples. The extent of disorder in the regrowth region was largest for the HCl sample with respect to the ClZ and wet etched samples. These microstructural and optical results suggest that the 1+ ion plays an important role in the generation of crystal defects during the RIE process. INTRODUCTION Reactive ion etching (RIE) is a preferred dry process step for fabrication of submicron III-V semiconductor device structures. This kinetically assisted chemical dry etch process offers several important advantages over other etching methods, namely etch anisotropy, etch rate control, selectively, accuracy, uniformity across the wafer and reproducibility [1]. As a result of these desirable characteristics, a number of semiconductor device designs involve RIE in their device fabrication process. Some of the more novel designs involve lateral quantum well arrays, whereby fabrication requires molecular beam epitaxial (MBE) regrowth on RIE semiconductors [2,3]. A major drawback of RIE is the potential lattice damage introduced by energetic ion bombardment and contamination. This material damage may lead to deterioration of device performance. It is important to identify and understand this RIE induced damage in order to develop and refine the RIE process, i.e. minimize crystal damage and thus optimize device performance. This study identifies and analyzes the damage associated with various RIE parameters used for quantum well fabrication. EXPERIMENTAL One micron of undoped GaAs was grown by MBE (Varion 360 MBE machine) on a semi-insulating GaAs substrate. The growth conditions were adjusted to achieve a growth rate of lum/hr with a substrate temperature of 6200 C. Preparation of substrates has been described elsewhere [4,53. Upon comple-
Mat. Res. Soc. Symp. Proc. Vol. 163. ' 1990 Materials Research Society
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tion of this initial growth
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