Paper EM-ThP2
Effect of Initial Substrate Conditioning on Structural and Optoelectronic Properties of In_xGa_1-xN Grown by MEPA-MOCVD

Thursday, November 10, 2016, 6:00 pm, Room Hall D

Fabrication of high quality Indium rich- In_1-xGa_xN layers is still a challenge due to the immiscibility between the binaries InN and GaN. The lack of lattice-matched substrate is an additional challenge for the growth of In_1-xGa_xN layers. The lattice mismatch between the substrate template and the In_1-xGa_xN layer generate residual strains and threading dislocations at the interface that propagate into the In_1-xGa_xN layers, and consequently, degrade the quality of the In_1-xGa_xN epilayer. To mitigate these effects, different approaches such as the use of buffer layers (e.g. GaN, InN, AlN) between the In_1-xGa_xN layers are explored.

In this contribution, we present our findings on the effects of substrate treatments on the structural and optoelectronic properties of In_1-xGa_xN layers grown by Migration-Enhanced, Plasma-Assisted MOCVD (MEPA-MOCVD). Furthermore, the analysis consist the data for In_1-xGa_xN layers grown on different nitrided sapphire substrates as well as layers grown on sapphire substrates templates, containing InN, GaN or AlN interlayers.

The optoelectronic properties – e.g. free carrier concentration, the mobility of the carriers, high-frequency dielectric constant ε_∞, and layer thickness in the In_1-xGa_xN layers have been analyzed by simulating the reflectance spectra, obtained via Fourier Transform Infra-red (FTIR) spectroscopy, using a multilayer stack model and a dielectric function based on Lorentz-Drude model. AFM topography has been used to study the surface morphology of the layers. Raman spectroscopy has been utilized to analyze the local crystallinity (E₂(high) mode) of the In_1-xGa_xN layers as well as the composition via the shift of the A₁(LO) mode and its broadening with In_1-xGa_xN target composition.