Nearly 4-Inch-Diameter Free-Standing GaN Wafer Fabricated by Hydride Vapor Phase Epitaxy with Pit-Inducing Buffer Layer

Abstract

A free-standing GaN wafer was fabricated by depositing a GaN buffer that induced the formation of pits (hereafter, pit-inducing GaN buffer) on a low-temperature-grown GaN buffer on the sapphire substrate. A high-temperature-grown GaN layer was grown on the pit-inducing GaN buffer that induced the formation of pits on the high-temperature-grown GaN layer. The pit-inducing buffer suppresses crack formation in the thick GaN film thereby releasing growth stress. Thermal stress in GaN on a sapphire system is also discussed on the basis of calculations utilizing a bilayer model. We have succeeded in the fabrication of a nearly 4-in.-diameter free-standing GaN thick wafer with a pit-inducing GaN buffer by one-stop hydride vapor phase epitaxy, which will lead to a low-cost fabrication of free-standing GaN wafers.

Deep Traps Spectra in Undoped Gan Films Grown by Hydride Vapor Phase Epitaxy Under Various Conditions

“…The growth process was performed in argon ambient with metallic Ga as a source material and hydrogen chloride and ammonia as active gases. The growth was performed at temperatures of 850-950°C that were somewhat lower than in a typical HVPE process of 1020-1050°C (Usikov et al, 2013;Sato et al, 2013;Fujito et al, 2009;Liu et al, 2014;Paskova et al, 2010) the growth rate was 0.2-1 µm/min and the total thickness of the layers was 10-20 µm. The growth was initiated at low growth rate and then continued with increased growth rate.…”

“…Similar dark spots defects could be detected in band edge MCL images of the samples. The dark spots/dislocation density indicates a reasonably high crystalline quality of the studied samples given that they are relatively thin in so far as the HVPE films go (dislocation densities below 10 6 cm −2 or even 10 4 cm −2 can be obtained for layers with thicknesses exceeding ~100 µm (Yoshida et al, 2008;Sato et al, 2013;Fujito et al, 2009). The diffusion length of non equilibrium charge carriers can be estimated from linear EBIC scans along the surface of the sample adjacent to the Schottky diode edge (Yakimov et al, 2008).…”

“…Hydride vapor phase epitaxy is a well-established growth technique for fabrication of Group III-Nitrides thick films and bulk crystals with good crystalline quality (Liu et al, 2014;Wu et al, 2013;Sato et al, 2013;Paskova et al, 2010;Fujito et al, 2009;Yoshida et al, 2008) The technique is quite versatile allowing to grow films and crystals of n-type (typically, by Si doping), p-type (by Mg doping) and semi-insulating (by deep levels Fe or Zn compensation) (Richter et al, 2013;Usikov et al, 2008;Lipski, 2010;Reshchikov et al, 2011). The growth rate can be varied from tens of nanometers per Science Publications AJAS hour to hundreds of microns per hour.…”

“…The growth rate can be varied from tens of nanometers per Science Publications AJAS hour to hundreds of microns per hour. The dislocation density can be made as low as 10 4 -10 7 cm −2 , depending on the layers thickness (Fujito et al, 2009;Sato et al, 2013). All this makes HVPE a very promising technique for fabrication of bulk GaN that can be used as substrates in nitrides epitaxy.…”

Blue to true green LEDs with semipolar quantum wells based on GaN nanostripes

“…These semipolar GaN quasi-substrates are commercially available but costly and small in size. Huge progress has been made [6] but the comparison to c-plane oriented pseudo-bulk [7] is still highly unfavorable. Consequently, heteroepitaxy of semipolar GaN based on cheap sapphire substrates remains important [8].…”