Two-step growth of high-quality GaN by hydride vapor-phase epitaxy

Abstract

The use of a low-temperature layer of GaN formed by hydride vapor-phase epitaxy (HVPE) as a template to grow high-quality HVPE films is demonstrated. Using layers formed by reacting GaCl and NH3 at 550 °C and annealed at a growth temperature of 1050 °C, thick films of GaN can be grown by HVPE with fewer than 108 dislocations per cm2. Dislocation densities measured by high-resolution x-ray diffraction, atomic-force microscopy step termination density and plan-view transmission electron miscroscopy reveal that ∼23 μm films have dislocation densities of ∼6×107 cm−2. Obtaining high-quality single-crystal character films was found to be dependent on several factors, most importantly, the rate of temperature increase to growth temperature and the layer thickness.

Direct Growth of GaN on (0001) Sapphire by Low Pressure Hydride Vapour Phase Epitaxy

“…FWHM values of w-rocking curves of 266 00 and of w/2q scans of 192 00 have been achieved. These values indicate the high crystalline quality achieved and compare well with results reported from GaN layers grown by HVPE [6] and MOVPE [3].…”

“…Thus, in this first step a crystalline layer which supplies high-density GaN seeds having the same orientation as the substrate is obtained. It has been reported in [6] that the heat-up process was found to be particulary critical for the buffer layer formation. SEM observation from interrupted heat-up processes have shown no remarkable change of the surface during the heat-up in our case.…”

“…However, the use of low-temperature GaN or AlN buffer layers in HVPE was found to result in polycrystalline or poor quality materials [3,5]. It is only recently, that a two-step process using rather complicated movements of the substrate to control the surface temperature has been reported to be successful in forming a low-temperature GaN buffer for subsequent growth of high-quality GaN layers in atmospheric pressure HVPE [6]. In this paper, we discuss our low-temperature GaN nucleation procedure on (0001) sapphire using a conventional HVPE reactor which allows reproducibly for subsequent growth of high-quality GaN layers.…”

Growth optimization for thick crack‐free GaN layers on sapphire with HVPE

“…Initially, a GaCl-pretreatment or a ZnO layer [1] were used to aid nucleation. Later low-temperature nucleation processes were established for direct growth on sapphire in HVPE [2]. However, lattice mismatch and thermal expansion differences result usually in cracks and wafer bending in thick GaN layers.…”

Optimization of low temperature GaN buffer layers for halide vapor phase epitaxy growth of bulk GaN

“…One alternative method, which does not require photolithography, is the two step deposition process involving growth of a low temperature (LT) GaN buffer layer. This technique has been used in both metal organic chemical vapor deposition (MOCVD) [15,16] and HVPE [17]. Using this technique, it has been shown that for thicker GaN layers (> 600 µm) the bulk GaN layer is spontaneously separated from the substrate which means that many time-consuming or complicated process steps such as mechanical lapping of sapphire [18], chemical etching [19], laser lift-off [20], ELOG [21,22] and void assisted separation [23] can be avoided.…”