Nanocomposites and nanomaterials

Formation of a homogeneous electron distribution profile in submicron GaAs epitaxial layers for ultra-high frequency devices
Krukovskyi S. I.,  Izhnin I.I.
 Scientific Research Company “Electron-Carat”, Stryjska St., 202, Lviv 79031, Ukraine.
E-mail: goro0609@gmail.com 

Most semiconductor devices are very sensitive to inhomogeneities, dislocations, point defects both in the active layer and at the interface of layers in the epitaxial structure. These material characteristics determine their reliability, stability and durability. When creating ultra-high frequency devices (such as Gunn diodes), which operate in the mode of limitation and accumulation of volume charge, the requirements for doping uniformity by thickness parameter of the active region are very strict. In addition, the area should be uncompensated and  with high mobility of charge carriers.
Rare earth and isovalent elements have a significant impact on defect formation processes. The former can effectively hetteronize the uncontrolled impurities in melts with the formation of chemical compounds, and the latter can restrict their access to the crystal lattice due to a decrease in the segregation coefficients. With certain ratios of rare earth and isovalent elements, a significant mutual enhancement of their gettering action is possible.
In the work is applied the complex technique of forming the properties of GaAs layers at low temperatures (500-600ºС). The technic combines the effect of doping with optimal Yb and Al ratios on the reduction of uncontrolled impurities  amount and modulation of the crystallization rate during growth. The technique is based on the dependence of the segregation coefficients of most impurities on the decrease of temperature rate during the growth of semiconductor epitaxial layers. Changing the rate of decrease in temperature can briefly reach 10ºC / min. The CV profilometry of charge carrier distribution in GaAs layers and their change under the simultaneous influence of Yb and Al doping and at different modes of crystallization rate modulation were investigated. The possibility of forming submicron GaAs layers with high electron homogeneity in thickness is shown.