GaAs Epitaxial Microrelief Layer

Abstract

It is a report about an epitaxial GaAs relief layer with 3 μ of thickness growth in Ga –AsCl3 – H2 system on n-GaAs (n=2x1018cm-3) substrate with multiple crystallization centers. Crystalline lattice on substrate surface is crystallographic disorientated with 3-5o of (100) to (110), treated in HCl:HNO3:H2O selective acid solution and thermally processed at 230-320 oC of temperature in vacuum 2 hours, then in inert medium with oxygen presence at 550-610 oC of temperature during 2-5 min. The epitaxial layer has a relief microstructure with 2,0-2,3 μ periodic dimensions and height from 80 nm to 180 nm, forming 110-120o at the top the angle. The relief layer morphology was studied with atomic force microscopy (AFM) and metallurgic microscopy MM500T. Reflection and absorption spectrum was obtained at variable incident angle (α=0; 5; 7; and 10o). In 0,54-1,22 μ spectrum range the perpendicular (α=0o) incident razes on micro-relief surface are reflected with 0,08-0,12%, absorption coefficient at λ=0,96 is 98 1/cm. A maximal jump of the reflected energy is observed at incident angle α=7o (11,06% la λ=0,65 μ and 39,05% la λ=1,12 μ), absorption diminishes up to 76,69 1/cm at incident angle α=10o. The micro-relief layer can be utilized in building of photovoltaic cells for concentrated solar energy.