In-Situ Pretreatment Approach for Surface Deterioration Alleviation Amidst Thermal Desorption of GaAs(100)
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J14.4.1
In-Situ Pretreatment Approach for Surface Deterioration Alleviation Amidst Thermal Desorption of GaAs(100) A.F. Pun1 , X. Wang1 , J.B. Meeks1 , S.M Durbin2 , and J.P. Zheng1 1 Department of Electrical and Computer Engineering, Florida A&M University and Florida State University, Tallahassee, FL, USA 2 Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, NEW ZEALAND ABSTRACT Within this study, a novel in-situ pretreatment is proposed theoretically and demonstrated experimentally, in which the formation of surface pits is subsequently stifled during thermal desorption. The proposed method involves fueling the well reviewed chemical oxide reduction reaction with a segregated source of material other than that ordinarily utilized in pit formation. The proposed method is implementable in virtually all deposition systems subject to the constraints of providing material deposition, substrate heating, and the creation of non-oxidizing environments either via vacuum or inert atmo sphere. INTRODUCTION As commonly subjected to thermal treatment with the intent of dislodging native oxide layers prior to epitaxial growth, gallium arsenide wafers endure surface deterioration characterized by the etched formation of surface pits. This pit generation has been the subject of much prior research, commonly characterizing such pits as 20-500 nm wide [1-3], 5-20 nm deep [1-5], and having surface densities of 108 -1010 cm-2 [2-5]. The formation of surface pits is an undesirable affect in device construction instigating the necessity for the manufacturer to grow micrometer-thick homoepitaxial buffer layers intended to smoothen the surface. However, such as the currently used technique is employed, it suffers from several deficiencies, including the utilization of significant time and material to deposit the buffer layer, which ultimately does not maintain the guaranteed elimination of propagating stacking faults. THEORY The composition of gallium arsenide native oxides has been well studied utilizing x-ray photo-spectroscopy (XPS), in which it has been revealed to consist of a large number of oxides. Such oxide species include Ga2 O [6-8], Ga2 O3 [6,9,10], As2 O3 [9,11], As2 O5 [12,13] and GaAsO 4 [14-19]. Further collaboration of these oxide species can be obtained from examination of the gallium-arsenic-oxide phase diagram developed at Bell Laboratories [13,20], in which the oxide is said to consist from interior to exterior of Ga2 O3 , As2 O3 , GaAsO 4 , and As2 O5 . GaAsO4 is not easily studied as the common As(3d) and Ga(3d) binding energy shifts (4.7 eV and 1.4 eV, respectively) directly overlap with Ga2 O3 and As2 O5 and distinguishing requires electron diffraction [17-19]. Further, As2 O5 is present only if very strong oxidation conditions are present during formation [21]. When the native oxide is heated, each of these species will decompose and/or evaporate according to established chemical paths. Ga2 O sublimes at temperatures above 500°C [22] requiring no outside material. However
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