Semipolar GaN grown on foreign substrates: a review

Abstract

Non-and semipolar GaN-based optoelectronic device structures have attracted much attention in recent years. Best results have been obtained on small bulk substrates cut from thick c-plane epi-wafers. However, owing to the limited size of such substrates, it is very attractive to study hetero-epitaxial approaches on foreign substrates. In this paper, we review the current state of such studies which eventually lead to large area non-or semipolar nitride structures. The simplest approach is to use planar sapphire or SiC wafers of non-c-plane orientations on which potentially less polar GaN can be grown. However, typically huge dislocation and in particular stacking fault densities evolve. More sophisticated approaches make use of the good GaN growth performance in the c-direction, eventually leading anyway to large area non-or semipolar structures. Several such approaches are discussed in this paper.

Structural, electronic, and optical properties ofm-plane InGaN/GaN quantum wells: Insights from experiment and atomistic theory

“…Also the intrinsic field leads to a spatial separation of electron and hole wave functions, causing a reduced radiative recombination rate [4,6], an effect that can be particularly undesirable for high-efficiency optoelectronic devices. To circumvent these effects arising from the intrinsic built-in fields, which fundamentally are caused by the growth along the polar c axis, significant research has been directed towards the fabrication of semi-and nonpolar structures [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In the case of semi-and nonpolar planes the c axis is at a nonvanishing angle with respect to the growth direction.…”

“…In the case of semi-and nonpolar planes the c axis is at a nonvanishing angle with respect to the growth direction. In semipolar planes residual built-in fields are expected and observed, even though these fields are significantly reduced [15,18]. In terms of built-in field reduction, nonpolar QW systems are ideal since in these structures the c axis lies in the growth plane.…”

Microstructure investigation of semi-polar (11-22) GaN overgrown on differently designed micro-rod array templates

“…1 In comparison with the (0001) polar orientation, InGaN/GaN based emitters grown along the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) direction are subjected to significantly reduced piezoelectric polarization fields, thus effectively increasing their internal quantum efficiency (IQE) by reducing the associated quantum confined stark effect (QCSE). [2][3][4] Furthermore, the (11-22) plane has been predicted to exhibit a lower indium chemical potential than either non-polar or polar surfaces, 5 making (11-22) GaN accommodate indium atoms more easily than either nonpolar or polar GaN. Consequently, (11-22) GaN becomes particularly important for achieving longer wavelength emission where high indium content is required.…”

Effects of substrate temperature, substrate orientation, and energetic atomic collisions on the structure of GaN films grown by reactive sputtering

“…2,6,10,11,14,15,51 Nevertheless, the obtained widths of the rocking curves were much broader than that found in the low-strain materials produced by MOCVD and MBE, which indicate a large density of defects in the analyzed films.…”

“…[1][2][3][4][5][6] In particular, the increasing use of light emitting diodes (LEDs) in a variety of lightning devices represents large-scale energy savings and considerable benefits to the environment. 5,[7][8][9] The main deposition techniques by which the highest quality films are produced with the highest control are molecular beam epitaxy (MBE) [10][11][12] and metalorganic chemical vapor deposition (MOCVD).…”