Surface, interfaces, thin films
Reduction of misfit dislocation density in metamorphic heterostructures by design optimization of the buffer layer with non-linear graded composition profile
M. Yu. Chernov,
V. A. Solov'ev,
S. V. Ivanov Ioffe Institute, St. Petersburg, Russia
Abstract:
Equilibrium distributions of misfit dislocation density along the growth direction of metamorphic buffer layers In
$_x$Al
$_{1-x}$As/GaAs with maximum In content
$x_{\mathrm{max}}\ge$ 0.77 and different non-linear graded composition profiles
$x\varpropto z^{1/n}$ are calculated. The effect of the initial In composition (
$n$ = 2) of In
$_x$Al
$_{1-x}$As buffer layer with convex-graded
$(x_{\mathrm{min}})$ composition profile on misfit dislocation density as well as amount of residual stresses at its top part is considered. Using computational approach, it was shown that a dislocation-free region is formed under thin tensile-strained GaAs layer (1–10 nm) inserted into InAlAs metamorphic buffer layer, which agrees with experimental data obtained early by transmission electron microscopy. Novel non-linear graded composition profile of metamorphic buffer layer has been proposed, which results in twice reduction of misfit dislocation density as compared to the convex-graded one. In addition, equilibrium distributions of misfit dislocation density in the HEMT heterostructures with two-dimensional electron channel In
$_x$Al
$_{1-x}$As, which are based on In
$_x$Al
$_{1-x}$As/GaAs metamorphic buffer layer of various designs, are calculated. The values of inverse steps
$(\Delta)$, representing the difference between the maximum In content of In
$_x$Al
$_{1-x}$As
$(x_{\mathrm{max}})$ and In content of In
$_{0.75}$Ga
$_{0.25}$As virtual substrate, at which relaxation of the elastic strains in 2D channel In
$_{0.75}$Ga
$_{0.25}$As/In
$_{0.75}$Al
$_{0.25}$As doesn't occur, are calculated for metamorphic buffer layers In
$_x$Al
$_{1-x}$As with convex-graded and optimized non-linear graded composition profiles.
Keywords:
metamorphic heterostructures, metamorphic buffer layer, misfit dislocations, elastic stresses, In(Ga,Al)As/GaAs. Received: 26.04.2023
Revised: 02.05.2023
Accepted: 02.05.2023
DOI:
10.21883/FTP.2023.03.55627.4915