Step‐Flow Growth of InN on N‐Polarity GaN Template by Molecular Beam Epitaxy with a Growth Rate of 1.3 μm/h

Abstract

The effects of substrate temperature and surface stoichiometry on the growth behavior of InN were investigated in molecular beam epitaxy with in situ monitoring by reflection high-energy electron diffraction and spectroscopic ellipsometry. InN was grown on nitrided sapphire substrate or N-polarity GaN template. For both cases, InN layers were found in N polarity by coaxial impact collision ion scattering spectroscopy. At growth temperatures ranging from 470 to 590 C, the N-rich condition was favorable for stable InN growth. Under the In-limited growth condition, the stepflow growth of InN was achieved on N-polarity GaN template at 580 C with a growth rate of 1.3 mm/h. The FWHMs of X-ray rocking curves around InN (002) and (102) Introduction InN, as an important III-nitride semiconductor, is attracting much attention with regard to extending the working wavelength of optoelectronic devices up to the orange and red region, as well as to developing high-frequency and high-power/ temperature electronic devices [1,2]. Compared with GaN and AlN, InN has the smallest effective electron mass, exhibits the highest peak drift velocity and has a peak overshoot velocity that lasts over the longest distances [2,3]. InN is expected to be a more suitable material for electronic devices such as high electron mobility transistors. However, InN has been less studied compared with GaN and its related alloys. To improve InN layer quality, several techniques have been tried, such as migration-enhanced epitaxy and the use of AlN buffer layers and GaN intermediate layers, but thick InN epilayers with high-quality and atomically flat surfaces are still difficult to achieve [4,5]. For molecular beam epitaxy (MBE) growth, substrate temperature and surface stoichiometry are two of the most important factors. In III-nitride systems we must also consider the significant effects of polarity on the epitaxy process.In the present work, the dependence of InN growth behavior on substrate temperature and surface stoichiometry was investigated in radio frequency plasma-assisted MBE. High crystal quality InN layers with good electrical properties were obtained on MBE-grown N-polarity GaN template.Step flow growth morphologies were observed even when the InN growth rate was as high as 1.3 mm/h. It was clearly shown that the InN layers were grown in N polarity.

Infrared measurements of InN films at low temperatures

“…It was estimated that the higher equilibrium vapour pressure of N and the lower decomposition temperature of InN lead to higher defect densities compared with AlN or GaN. It was found that the anion polarity crystal has higher quality [1]. Recently single crystals were found to have a bandgap energy below 1 eV.…”

In-rich InGaN∕GaN quantum wells grown by metal-organic chemical vapor deposition

“…Based on the indium compositional profile in In-rich InGaN layer, we calculated energy levels and envelope functions by Fourier series method in In-rich InGaN/ GaN SQW with compositional grading and we could explain nearultraviolet ͑UV͒ emission observed from the SQW. 10 We obtained In-rich InGaN/ GaN SQWs at relatively high growth temperature, compared with previous reports, [1][2][3][4] and at high TMIn flow rate. There existed thickness fluctuations and many structural defects in as-grown InGaN as well as in subsequently grown low temperature ͑LT͒-capped GaN.…”

“…[1][2][3][4] Although thermal instability of InN as well as large lattice and thermal mismatches make the growth of high quality InN films extremely difficult, 5 more recent results on InN growth are strongly positive and indicative of potential device applications. 6,7 In this case, InN and In-rich nitrides are important constituents in devices such as light emitting diodes ͑LEDs͒, high electron mobility transistors ͑HEMTs͒, and solar cells so that the growth of two-dimensional ͑2D͒ InN and In-rich nitrides on GaN substrate is inevitable.…”

Properties of the fundamental absorption edge of InN crystals investigated by optical reflection and transmission spectra

“…Epitaxial layers were grown at 580-630 °C on an InN or GaN buffer layer grown around 450 °C. The nitrogen polarity was found by coaxial impact collision ion scattering spectroscopy (CAICISS) measurements [4]. Hall measurements were performed at room temperature (RT).…”