Characterising the degree of polarisation anisotropy in an a ‐plane GaN film

Abstract

We have performed a thorough characterisation of an a ‐plane GaN film, using X‐ray diffraction reciprocal space mapping, k·p theory and polarised photoluminescence spectroscopy Within the plane of the film and along the growth direction, the strain was found to be compressive and tensile respectively. The relative oscillator strength of the transitions involving the topmost valence bands has been calculated as a function of strain. We find that using the experimentally determined strain values as input parameters to the theoretical model, results in good agreement between the predicted relative oscillator strengths and the degree of optical polarisation anisotropy measured in the low temperature photoluminescence spectroscopy. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In-Plane Optical Anisotropy of a -Plane GaN Film on r -Plane Sapphire Grown by Metal Organic Chemical vapour Deposition

“…As a result, the energy difference between the LH band and the SCH band enhances, which can be reflected by the increasing PL peak-shift value in Table 1. Badcock et al [19] have observed a slightly similar PL peak-shift about 2 meV in a 5 μm a-plane GaN film at T = 6 K, which is much smaller than the results shown in Table 1 (>10 meV). This can be explained by the fact that the thickness of their sample is much thicker than that of ours and the in-plane strain is almost relaxed.…”

“…Therefore the optical properties of non-polar GaN have been extensively studied both theoretically and experimentally. [11−18] For experimental studies, the optical anisotropic characteristics of a-plane GaN have been observed by Badcock et al, [19] Jia et al [20] and Wu et al, [21] systematically investigated at low temperatures by Paskov et al [22] In this Letter, the optical anisotropy of a-plane GaN films is studied in detail through polarised photoluminescence (PL) and optical transmission measurements. The shift of a polarised PL peak reaches up to 17.7 meV at room temperature.…”

“…Meanwhile, with increasing strain, the LH band moves up more rapidly than the SCH band. [19,21] Thus, the polarised PL spectrum of E c corresponds to the electron-hole recombination process between CB and SCH bands, the one of E⊥c corresponds to the process between CB and the higher LH band. Therefore, the PL peak-shift reveals the energy difference between the SCH band and LH band.…”