Semipolar GaN‐based heterostructures on foreign substrates

Abstract

This paper reviews our recent investigations about semipolar GaN‐based optoelectronic heterostructures grown on foreign substrates. Two basically different approaches are discussed, both making use of epitaxial growth in the polar c‐direction to minimize any crystalline defects. By selective area growth, stripes with triangular cross‐section have been formed with semipolar side‐facets, on which quantum well and electroluminescence test structures have been deposited. By careful optimisation of many growth parameters, we could drastically increase the growth temperature of GaInN quantum wells emitting beyond 500 nm. In the second approach, the GaN growth starts on inclined sapphire c‐planes, which form the side facets of trenches etched into the substrates. After coalescence, planar semipolar GaN layers can be achieved. We investigated various sapphire wafer orientations leading to {112‾2}, {101‾1}, and {202‾1} layers. After careful optimisation with a major focus on the decrease of the stacking fault density, we have also investigated the doping behaviour of such semipolar structures. Eventually, full electroluminescence test structures could be grown.

Optimization of the quality control parameters in sapphire single crystal preparation using the Kyropoulos method

“…[1][2][3] At present, it is widely used as a substrate for manufacturing LED devices, 4 and the biggest challenge of the LED market is to produce large-sized and high-quality sapphire crystals at low cost. 5 The Kyropoulos (Ky) 6 method is mainly used for preparing large-diameter and high-quality single crystal sapphire. Seeding is the first step of sapphire preparation, whose quality directly affects the growth quality of subsequent sapphire crystals.…”

A Novel Defect Diagnosis Method for Kyropoulos Process-Based Sapphire Growth

“…Sapphire has been used in many fields. C-plane sapphire is the ideal material for making light-emitting diodes (LEDs) [2] and sapphire can be used for bearing surfaces [3]. Kyropoulos (Ky) method is one of common methods for preparing sapphire [4], which is widely used because of its relatively low production cost.…”

“…Kim [6] proposed the use of image processing technology to develop an automatic seeding system in the process of growing the sapphire crystal by the Ky method. Yu [7] proposed the OCS method to detect the seeding point in the stage (2). Regarding the important stage (4) only human inspection is performed.…”

Polarization‐field control in nitride light emitters

“…3, March 2011). Two Feature Articles present some overview over this field, one (Scholz et al) concentrating on various approaches how to obtain semipolar heterostructures, the other (Leung et al) critically comparing various semipolar directions grown on patterned sapphire substrates, which otherwise are difficult to obtain, and their potential for optoelectronic device applications. The majority of the other papers is nicely balanced between epitaxial growth issues and sophisticated characterization tools.…”