Optimization of AlGaN/GaN/Si(111) buffer growth conditions for nitride based HEMTs on silicon substrates

• We investigate the influence of structure of LT-AlN/HT-GaN buffers on the electrical properties of grown AlGaN/AlN/buffer/Si(111) heterostructures.
• We examine the impact of HT-GaN layer growth conditions (V/III mole ratio) on the optical and electrical properties of AlGaN/AlN/buffer/Si(111) heterostructures..
• We have compared the electrical parameters of heterostuctures grown on c-plane sapphire and Si(111) substrates.

In this work we present results regarding growth of AlGaN/GaN/Si(111) HEMTs for integration of high frequency microelectronics with a silicon platform. GaN buffers with thicknesses above 1 μm were grown using one or two low temperature LT-AlN interlayers. The impact of the number of LT-AlN interlayers as well as the influence of the V/III ratio during growth of the GaN buffer, on the surface morphology and electrical parameters of AlGaN/AlN/GaN/Si(111) heterostructures were studied.Obtained results show that application of low temperature AlN interlayers during growth of GaN on Si(111) is a valuable method of stress reduction in the deposited GaN layer and thus extends its critical thickness. However, deposition of a LT-AlN layer leads to a surface roughness and a decrease of GaN buffer resistivity. Growth of the GaN buffer with high V/III ratio enhances the buffer resistivity, 2DEG mobility and sheet carrier concentration. Optimized AlGaN/AlN/GaN/Si(111) heterostructure has similar mobility and sheet carrier concentration as a reference AlGaN/AlN/GaN heterostructure grown on sapphire.