Observation of self-assembled InGaN/GaN superlattice structure grown on N-polar GaN by plasma-assisted molecular beam epitaxy

K Khan,C Wurm,S Diez,E Ahmadi,Kai Sun,U K Mishra

doi:10.1063/5.0063285

K Khan, C Wurm + Show 4 more

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https://doi.org/10.1063/5.0063285

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Abstract

In this paper, we report on the observation of self-assembled InGaN/(In)GaN superlattice (SL) structure in a nominal “InGaN” film grown on N-polar GaN substrate. 350 nm thick InGaN films were grown at different temperatures ranging from 600 to 690 °C. Structural characterization was conducted via atomic force microscopy, scanning transmission electron microscopy, high-resolution x-ray diffraction, and XRD reciprocal space map. A SL structure was unexpectedly observed on all samples. However, the In content in each layer varied depending on growth temperature. By increasing the substrate temperature to 670 °C, a periodic structure composed of 3 nm In0.26Ga0.74N and 3 nm of GaN with a surface roughness of ∼0.7 nm was achieved. This work establishes a method for the growth of InGaN films with high structural quality on N-polar GaN and opens a new pathway for the design and fabrication of various electronic and optoelectronic devices with enhanced performance.

Highlights

In this letter, we report on the growth of 350 nm-thick Npolar InGaN film with an average InN mole fraction of ∼13% with high structural quality and sub-nm surface roughness
We show that the composition of the superlattice structure changes by varying the growth temperature
A JEOL JEM-3100R05 electron microscope with a cold-field emission gun equipped with both a probe and an imaging corrector was used for atom-resolved imaging that was operated in STEM mode

Summary

Introduction

We report on the growth of 350 nm-thick Npolar InGaN film with an average InN mole fraction of ∼13% with high structural quality and sub-nm surface roughness. This surface rms for sample D is significantly lower than that of any previously reported Npolar InGaN films with similar In content.20,21 A smooth surface morphology was maintained by further increasing the growth temperature to 690 ○C. The high-magnification STEM-HAADF image on this sample [Fig. 3(b)] revealed a SL structure with a period of ∼5.9 nm, which is similar to that extracted from the HRXRD ω-2θ profile.

Results

Conclusion