Abstract
Non-polar (11–20) GaN with significantly improved crystal quality has been achieved by means of overgrowth on regularly arrayed micro-rod templates on sapphire in comparison with standard non-polar GaN grown without any patterning processes on sapphire. Our overgrown GaN shows massively reduced linewidth of X-ray rocking curves with typical values of 270 arcsec along the [0001] direction and 380 arcsec along the [1–100] direction, which are among the best reports. Detailed X-ray measurements have been performed in order to investigate strain relaxation and in-plane strain distribution. The study has been compared with the standard non-polar GaN grown without any patterning processes and an extra non-polar GaN sample overgrown on a standard stripe-patterned template. The standard non-polar GaN grown without involving any patterning processes typically exhibits highly anisotropic in-plane strain distribution, while the overgrown GaN on our regularly arrayed micro-rod templates shows a highly isotropic in-plane strain distribution. Between them is the overgrown non-polar GaN on the stripe-patterned template. The results presented demonstrate the major advantages of using our regularly arrayed micro-rod templates for the overgrowth of non-polar GaN, leading to both high crystal quality and isotropic in-plane strain distribution, which is important for the further growth of any device structures.
Highlights
There is a significantly increasing demand on III-nitride based power electronics and radio-frequency (RF) devices required for 5G mobile communications, as GaN exhibits major advantages in fabricating high power, high frequency and high temperature devices due to its intrinsically high breakdown voltage, high saturation electron velocity and excellent mechanical hardness1,2
Based on the well-established experience built on the growth and fabrication of AlGaAs/GaAs high electron mobility transistors (HEMTs), a simple but promising solution is to grow an AlGaN/GaN heterostructure with modulation doping along a non-polar direction, where the polarisation can be eliminated and the sheet carrier density of 2DEG can be tuned through optimising the doping level in AlGaN barrier6
We present a detailed study of strain relaxation of our (11–20) non-polar GaN with high crystal quality which has been achieved by means of overgrowth on our regularly arrayed micro-rod templates
Summary
There is a significantly increasing demand on III-nitride based power electronics and radio-frequency (RF) devices required for 5G mobile communications, as GaN exhibits major advantages in fabricating high power, high frequency and high temperature devices due to its intrinsically high breakdown voltage, high saturation electron velocity and excellent mechanical hardness1,2. We developed a cost-effective approach for the overgrowth of (11–22) semi-polar GaN on m-plane sapphire by using regularly arrayed micro-rod templates, leading to substantial improvement in crystal quality.
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