The influence of substrate polarity on the structural quality of InN layers grown by high-pressure chemical vapor deposition

Abstract

The influence of substrate polarity on the properties of InN layers grown by high-pressure chemical vapor deposition has been studied. The 2Θ-ω x-ray diffraction scans on InN layers deposited on polar GaN epilayers revealed single-phase InN(0002) with a full width at half maximum (FWHM) of around 200arcsec. InN layers grown on N-polar GaN exhibit larger FWHMs. Rocking curve analysis confirmed single-phase InN for both growth polarities, with FWHM values for ω-RC(002) at 2080arcsec for InN grown on Ga-polar templates. The A1(LO) Raman mode analysis shows higher free carrier concentrations in InN grown on N-polar templates, indicating that polarity affects the incorporation of impurities.

Search for free holes in InN:Mg-interplay between surface layer and Mg-acceptor doped interior

“…This observation can be not statistically relevant, however, some reports indicate that N-polar undoped InN samples have higher apparent free electron concentration than In-polar ones grown at the same conditions and that the polarity of the substrate affects the incorporation of impurities. 11,19 Thus, one cannot exclude that In-polarity is propitious for p-type InN.…”

Optical properties of InN grown on templates with controlled surface polarities

“…Additionally, for sample B the FWHM of the A 1 (LO) decreases. Line shape calculations reveal a decrease of the carrier concentration from 4.2 × 10 18 to 2.5 × 10 18 cm −3 , respectively 16. This also indicates lower impurity incorporation due to the Ga‐polar substrate.…”

“…Details about the growth process can be found elsewhere 18. XRD measurements revealed for these sample single phase InN(0002) with hexagonal symmetry 16.…”

“…Typical substrate templates for InN are sapphire, ZnO or GaN 13, with GaN/sapphire templates providing the best conditions for high quality InN layers due to a low lattice mismatch and availability. However, the influence of the substrate polarity and the polarity of the layer itself on the optical and structural properties is investigated only marginal, especially for high‐pressure CVD grown samples 16. We will demonstrate that the use of polarity controlled GaN/sapphire substrates leads to unstrained layers with good structural and optical properties.…”

Advantage of In- over N-polarity for disclosure of p-type conduction in InN:Mg

“…The latter problem has already been adressed in undoped n-type InN-the influence of growth polarity was studied from the point of view of interface/interlayer-related electron density, morphology, and growth mode of InN. 2,[12][13][14][15][16] The investigations relied among others on the studies of apparent Hall density as a function of InN layer thickness (i.e., the function of bulk electrons contribution) for In-and N-growth polarity. In Refs.…”