Band-GaP Energy and Physical Properties of InN Grown by RF-Molecular Beam Epitaxy

Abstract

This paper describes studies on high-quality InN growth on sapphire by RF-MBE. Critical procedures to obtain high-quality InN films were investigated and (1) nitridation process of sapphire substrates prior to growth, (2) precise control of V/III ratio and (3) selection of optimum growth temperature were found to be essential. Detailed structural characterizations by XRD, TEM, Raman scattering and EXAFS indicate that InN films obtained in this study have ideal hexagonal wurtzite structure. FWHMs of ω-2θ mode XRD and E 2 (high)-phonon-mode of Raman scattering are as small as 28.9 arcsec and 3.2 cm -1 , respectively. True band gap energy of InN is also discussed based on optical characterization results obtained from well-characterized hexagonal InN grown in this study. PbS, instead of InGaAs, was used as a detector for PL study in order to solve the problem coming from the cut-off wavelength of InGaAs detector. Based on these systematic studies on structural and optical property characterizations using high-quality InN, true band-gap energy of InN is suggested to be less than 0.67 eV and approximately 0.65 eV at room temperature. Single-crystalline InN films are also successfully grown on Si substrates by a brief nitridation of the Si substrates. Significant improvement of InN crystal quality on Si substrates by the insertion of an AlN buffer layer is also demonstrated.

Growth of high-quality InN films by insertion of high-temperature InN buffer layer

“…The reasons for this increase are the realization of high-quality single-crystalline InN films and the subsequent discussion on band gaps in these high-quality films. The band gap of InN has been recently recognized to be less than 0.67 eV [1], much smaller than the previously reported value of approximately 1.9 eV [2,3], by investigating the obtained high-quality InN films. For the decision of the real band-gap value of InN and the realization of InN-based devices, however, further improvement in crystal quality is required.…”

“…These values were calculated by referring to the report by Heinke et al [12] The values were almost the same; the improvement of the twist distribution by inserting the HT-InN buffer layer was not observed. For further improvement of the InN film quality, we have to solve the problem of twist distribution [1]. This should be due to the large lattice mismatch over 10%, which is for the AlN layer formed on the substrate surface by nitridation.…”

InN layers grown on silicon substrates: effect of substrate temperature and buffer layers

“…1a). This effect indicates that the dissociation temperature of InN is lower than the temperature needed to desorb the excess indium, as it has previously been reported by other authors [8][9][10]. In order to avoid this phenomenon, the substrate growth temperature is pointed out as the first critical parameter to be selected.…”

A‐plane (11$ \bar 2 $0) InN growth on nitridated R‐plane (10$ \bar 1 $2) sapphire by ECR‐MBE

“…Therefore, growth techniques of high quality wurtzite InN (h-InN) in direction of c-axis and its properties have been extensively studied, leading to the discussion of the band gap energy around 0.65 eV [1][2][3][4][5][6][7]. However, it is well-known that c-axis oriented optoelectronic devices suffer from large piezoelectric polarization field in particular, and it results in the low electron-hole recombination efficiency.…”