Effects of off-axis GaN substrates on optical properties of m-plane InGaN/GaN light-emitting diodes

Effect of m-plane GaN substrate miscut on InGaN/GaN quantum well growth

“…Theoretical studies suggested that the undesired internal fields can be avoided by fabricating devices on nonpolar surface perpendicular to c-plane, i.e., m-plane {1 1 0 0} or a-plane {1 1 2 0} [4]. In the last few years, the growth of III-nitrides in nonpolar direction, so-called nonpolar nitrides, has drawn considerable research interest due to its potential to improve the light efficiencies of optoelectronic devices [6][7][8][9][10][11][12]. All the theoretical and experimental reports showed that growth and device design with active regions parallel to the nonpolar crystallographic planes is a promising approach to achieve enhanced emission, especially in the green region, which has been problematic for a long time [13].…”

“…It was previously reported that emission intensities and wavelengths from m-plane InGaN QWs were highly sensitive to the miscut angles of GaN substrates [12]. Namely, the peak wavelength from m-plane LEDs was found to be shifted by $ 60 nm for a substrate miscut angle of 51 toward the [0 0 0 1] (c À -axis) direction [12]or the [1 1 2 0] (a-axis) direction [6] with respect to that of on-axis structure.…”

“…Namely, the peak wavelength from m-plane LEDs was found to be shifted by $ 60 nm for a substrate miscut angle of 51 toward the [0 0 0 1] (c À -axis) direction [12]or the [1 1 2 0] (a-axis) direction [6] with respect to that of on-axis structure. On the other hand, there have been no reports on the effect of increasing the miscut angles simultaneously toward the [0 0 0 1] (c + -axis) and [1 1 2 0] (a-axis) directions.…”

Effect of carrier gas and substrate misorientation on the structural and optical properties of m-plane InGaN/GaN light-emitting diodes

“…Despite the encouraging nature of these results, they contradict earlier reports linking enhanced indium incorporation efficiency in m-plane InGaN-based QWs to substrate misorientation toward the [0 0 0 1 ] c À direction. However, the GaN:Si thin films in those studies were grown using H 2 as the carrier gas, resulting in surfaces with moderate faceting and/or a high density of lateral surface undulations [21,22]. Indeed, similar results have been observed on intentionally faceted surfaces, with varying degrees of indium incorporation efficiency occurring on different microfacets [31].…”

“…Initial studies on InGaN/GaN LEDs grown on free-standing m-plane substrates used nominally on-axis substrates [20]. More recent investigations found that growth on substrates misoriented toward the [0 0 0 1 ] c À direction could be used to improve the surface morphology, but morphological data was presented only for relatively large misorientation angles of 51 and 101 [15,21,22]. In addition, studies by Yamada et al [21,22] concluded that the indium incorporation efficiency in m-plane InGaN-based QWs was much lower than c-plane InGaN-based QWs grown under similar conditions and that substrate misorientation toward the [0 0 0 1 ] c À direction could be used to increase the indium incorporation efficiency and the peak emission wavelength of m-plane InGaN-based QWs.…”