Surface Morphology Of Heterostructures Research Articles

Study of Interface of Ohmic Contacts to AlGaN/GaN Heterostructure

The paper embraces studies of the interface of ohmic contacts and AIIIBV-N heterostructure. The TiAl based metallization stack was investigated. The Ti/Al/Ni/Au contact to AlGaN/GaN heterostructures fabricated by metal-organic vapour phase epitaxy was examined using three methods i.e. etching of annealed contact metallization, fractures (prepared at room temperature and after a bath in liquid nitrogen) and microsections imaging. The main focus was on the estimation of reaction range on the metal-semiconductor interface of samples. In the first method, the surface of AlGaN/GaN heterostructure after etching of metallization was studied by an optical microscope, scanning electron microscope and atomic force microscope. The changes of surface morphology of heterostructure directly reflect solid state reactions range between metallization and semiconductor. The range of reactions was also observed using the small-angle microsections method while the fractures analysis did not bring valuable information.

Rol' mekhanichnykh napruzhen' pry ionniy implantatsiyi tverdykh rozchyniv CdHgTe

The properties of n-CdxHg1 xTe/CdZnTe (x = 0.223) structures implanted with B+ and Ag+ ions with an energy of 100 keV to a dose of 3 x 10^13 cm^-2 are studied. The software package TRIM_2008 was applied to simulate the ion implantation process. The surface morphology of heterostructures and their optical, mechanical and electrical properties are studied. It is found that the ion irradiation of specimens gives rise to the formation of a characteristic relief on their surface, as well as a layer in the near-surface region, where the optical parameters differ from those in the matrix. The implantation of CdxHg1 xTe epitaxial layers with boron and silver ions with the same energy and to the same dose brings about the formation of a damaged layer, substantially non-uniform by the thickness and the damage character, with maximum mechanical stresses that differ by two orders of magnitude. The values of the crystal lattice contraction coefficient b and the mechanical stresses omax in the region of radiation-induced disordering in the solid solution are determined. The influence of mechanical stresses in the doped layer on the defect redistribution and the formation of properties of Cd0:223Hg0:777Te after the implantation is discussed.