[1] H HARIMA. Properties of GaN and related compounds studied by means of Raman scattering. Journal of Physics: Condensed Matter, R967(2002).

[3] Y M ZHANG, J F WANG, D M CAI et al. Growth and doping of bulk GaN by hydride vapor phase epitaxy. Chinese Physics B, 026104(2020).

[6] P S HSU, K M KELCHNER, A TYAGI et al. InGaN/GaN blue laser diode grown on semipolar (30¯31) free-standing GaN substrates. Applied Physics Express, 052702(2010).

[7] A S ABBAS, A Y ALYAMANI, S NAKAMURA et al. Enhancement of n-type GaN (20¯21) semipolar surface morphology in photo-electrochemical undercut etching. Applied Physics Express, 036503(2019).

[8] M BOCKOWSKI, M IWINSKA, B AMILUSIK et al. Doping in bulk HVPE-GaN grown on native seeds-highly conductive and semi-insulating crystals. Journal of Crystal Growth, 499:, 1(2018).

[9] V V VORONENKOV, N I BOCHKAREVA, R I GORBUNOV et al. Two modes of HVPE growth of GaN and related macrodefects. Physica Status Solidi C, 468471(2013).

[10] M LEE, S PARK. Stress-engineered growth of homoepitaxial GaN crystals using hydride vapor phase epitaxy. RSC Advances, 35571(2018).

[11] L ZHANG, Y SHAO, X HAO et al. Improvement of crystal quality HVPE grown GaN on an H₃PO₄ etched template. CrystEngComm, 5001(2011).

[12] V V VORONENKOV, Y S LELIKOV, A S ZUBRILOV et al. Thick GaN film stress-induced self-separation. IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering, St. Petersburg and Moscow, 833(2019).

[13] M MYNBAEVA, A TITKOV, A KRYZHANOVSKI et al. Strain relaxation in GaN layers grown on porous GaN sublayers. Materials Research Society Internet Journal of Nitride Semiconductor Research, 1(1999).

[14] S DING, Y W LI, X Q XIU et al. Comparison study of GaN films grown on porous and planar GaN templates. Chinese Physics B, 038103(2020).

[15] N LIU, Y JIANG, J XIAO et al. Fabrication of 2-inch free- standing GaN substrate on sapphire with a combined buffer layer by HVPE. Frontiers in Chemistry, 9:, 671720(2021).

[16] T KIM, Y H JUNG, J SONG et al. High-efficiency, microscale GaN light-emitting diodes and their thermal properties on unusual substrates. Small, 1643(2012).

[17] X L TONG, L LI, D S ZHANG et al. The influences of laser scanning speed on the structural and optical properties of thin GaN films separated from sapphire substrates by excimer laser lift-off. Journal of Physics D: Applied Physics, 045414(2009).

[18] J KIM, J H KIM, S H CHO et al. Selective lift-off of GaN light-emitting diode from a sapphire substrate using 266-nm diode-pumped solid-state laser irradiation. Applied Physics A, 1(2016).

[19] C F CHU, F I LAI, J T CHU et al. Study of GaN light-emitting diodes fabricated by laser lift-off technique. Journal of Applied Physics, 3916(2004).

[20] P R TAVERNIER, D R CLARKE. Mechanics of laser-assisted debonding of films. Journal of Applied Physics, 1527(2001).

[21] T UEDA, M ISHIDA, M YURI. Separation of thin GaN from sapphire by laser lift-off technique. Japanese Journal of Applied Physics, 041001(2011).

[22] H FUJIKURA, T KONNO, T SUZUKI et al. Macrodefect-free, large, and thick GaN bulk crystals for high-quality 2-6 in. GaN substrates by hydride vapor phase epitaxy with hardness control. Japanese Journal of Applied Physics, 065502(2018).

[23] S FUJIMOTO, H ITAKURA, T TANIKAWA et al. Growth of GaN and improvement of lattice curvature using symmetric hexagonal SiO₂ patterns in HVPE growth. Japanese Journal of Applied Physics, SC1049(2019).

[24] T YOSHIDA, M SHIBATA. GaN substrates having a low dislocation density and a small off-angle variation prepared by hydride vapor phase epitaxy and maskless-3D. Japanese Journal of Applied Physics, 071007(2020).

[25] Y MIKAWA, T ISHINABE, Y KAGAMITANI et al. Recent progress of large size and low dislocation bulk GaN growth. Gallium Nitride Materials and Devices XV, 11280:, 1128002(2020).

[26] J H SHIM, J S PARK, J G PARK. A bow-free freestanding GaN wafer. RSC Advances, 21860(2020).

[28] L LIU, R YU, G WANG et al. Fabrication of a 2 inch free standing porous GaN crystal film and application in the growth of relaxed crack-free thick GaN. CrystEngComm, 7245(2021).

[29] R YU, G WANG, Y SHAO et al. From bulk to porous GaN crystal: precise structural control and its application in ultraviolet photodetectors. Journal of Materials Chemistry C, 14116(2019).

[30] L ZHANG, Y DAI, Y WU et al. Epitaxial growth of a self- separated GaN crystal by using a novel high temperature annealing porous template. CrystEngComm, 9063(2014).

[31] L LIU, X ZHANG, S WANG et al. Nucleation mechanism of GaN crystal growth on porous GaN/sapphire substrates. CrystEngComm, 1840(2022).

[32] L L CAI, C J FENG. First-principles study on the electronic structure and optical properties of GaN with Mg doped. Journal of North China Institute of Science and Technology, 120(2019).

[33] Z XIE, Y SUI, J BUCKERIDGE et al. Demonstration of the donor characteristics of Si and O defects in GaN using hybrid QM/MM. Physica Status Solidi (A), 1600445(2017).

[34] J A FREITAS. Pervasive shallow donor impurities in GaN. ECS Journal of Solid State Science and Technology, 015009(2019).

[35] R P VAUDO, X XU, A D SALANT et al. Background impurity reduction and iron doping of gallium nitride wafers. MRS Online Proceedings Library (OPL), 743:, 207(2002).

[36] F LIPSKI. Si-doped GaN by Hydride-vapour-phase-epitaxy Using a Ga: Si-solution as Doping Source. Annual Report, Institute of Optoelectronics, Ulm University, 53(2007).

[37] E RICHTER, C HENNIG, U ZEIMER et al. N-type doping of HVPE-grown GaN using dichlorosilane. Physica Status Solidi (A), 1658(2006).

[38] M IWINSKA, T SOCHACKI, M AMILUSIK et al. Homoepitaxial growth of HVPE-GaN doped with Si. Journal of Crystal Growth, 456:, 91(2016).

[39] T MARKURT, L LYMPERAKIS, J NEUGEBAUER et al. Blocking growth by an electrically active subsurface layer: the effect of Si as an antisurfactant in the growth of GaN. Physical Review Letters, 036103(2013).

[40] J XIE, S MITA, L HUSSEY et al. On the strain in n-type GaN. Applied Physics Letters, 141916(2011).

[41] S FRITZE, A DADGAR, H WITTE et al. High Si and Ge n-type doping of GaN doping-limits and impact on stress. Applied Physics Letters, 122104(2012).

[42] E RICHTER, T STOICA, U ZEIMER et al. Si doping of GaN in hydride vapor-phase epitaxy. Journal of Electronic Materials, 820(2013).

[43] S Y XIA, Y M ZHANG, J F WANG et al. HVPE growth of bulk GaN with high conductivity for vertical devices. Semiconductor Science and Technology, 014009(2021).

[44] Y OSHIMA, T YOSHIDA, K WATANABE et al. Properties of Ge-doped, high-quality bulk GaN crystals fabricated by hydride vapor phase epitaxy. Journal of Crystal Growth, 3569(2010).

[45] M WIENEKE, H WITTE, K LANGE et al. Ge as a surfactant in metal-organic vapor phase epitaxy growth of a-plane GaN exceeding carrier concentrations of 1020 cm^-3. Applied Physics Letters, 012103(2013).

[46] P BOGUSŁAWSKI, J BERNHOLC. Doping properties of C, Si, and Ge impurities in GaN and AlN. Physical Review B, 9496(1997).

[47] M IWINSKA, N TAKEKAWA, V Y IVANOV et al. Crystal growth of HVPE-GaN doped with germanium. Journal of Crystal Growth, 480:, 102(2017).

[48] Y M ZHANG, J F WANG, X J SU et al. Investigation of pits in Ge-doped GaN grown by HVPE. Japanese Journal of Applied Physics, 120910(2019).

[49] A USIKOV, O KOVALENKOV, V SOUKHOVEEV et al. Electrical and optical properties of thick highly doped p-type GaN layers grown by HVPE. Physica Status Solidi (c), 1829(2008).

[50] S NAKAMURA, N IWASA, M S M SENOH et al. Hole compensation mechanism of p-type GaN films. Japanese Journal of Applied Physics, 1258(1992).

[51] H AMANO, M KITO, K HIRAMATSU et al. P-type conduction in Mg-doped GaN treated with low-energy electron beam irradiation (LEEBI). Japanese Journal of Applied Physics, L2112(1989).

[52] Y Z TONG, F LI, Z J YANG et al. Electrical property and annealing characteristics of heavy Mg-doped GaN films. Semiconductor Optoelectronics, 140(2001).

[53] K OHNISHI, Y AMANO, N FUJIMOTO et al. Halide vapor phase epitaxy of p-type Mg-doped GaN utilizing MgO. Applied Physics Express, 061007(2020).

[54] T KIMURA, K OHNISHI, Y AMANO et al. Thermodynamic analysis of the gas phase reaction of Mg-doped GaN growth by HVPE using MgO. Japanese Journal of Applied Physics, 088001(2020).

[55] K OHNISHI, Y AMANO, N FUJIMOTO et al. Electrical properties and structural defects of p-type GaN layers grown by halide vapor phase epitaxy. Journal of Crystal Growth, 566:, 126173(2021).

[56] L T ROMANO, M KNEISSL, J E NORTHRUP et al. Influence of microstructure on the carrier concentration of Mg-doped GaN films. Applied Physics Letters, 2734(2001).

[57] N TETSUO, I NOBUYUKI, T KAZUYOSHI et al. Wide range doping control and defect characterization of GaN layers with various Mg concentrations. Journal of Applied Physics, 165706(2018).

[58] M HORITA, S TAKASHIMA, R TANAKA et al. Hall-effect measurements of metalorganic vapor-phase epitaxy-grown p-type homoepitaxial GaN layers with various Mg concentrations. Japanese Journal of Applied Physics, 031001(2017).

[59] R HEITZ, P MAXIM, L ECKEY et al. Excited states of Fe³⁺ in GaN. Physical Review B, 55:, 4382(1997).

[60] M IWINSKA, R PIOTRZKOWSKI, E LITWIN-STASZEWSKA et al. Highly resistive C-doped hydride vapor phase epitaxy-GaN grown on ammonothermally crystallized GaN seeds. Applied Physics Express, 011003(2016).

[61] JR J A FREITAS, J G TISCHLER, J H KIM et al. Properties of Fe-doped semi-insulating GaN substrates for high-frequency device fabrication. Journal of Crystal Growth, 403(2007).

[62] M IWINSKA, R PIOTRZKOWSKI, E LITWIN-STASZEWSKA et al. Crystallization of semi-insulating HVPE-GaN with solid iron as a source of dopants. Journal of Crystal Growth, 475:, 121(2017).

[63] M IWINSKA, M ZAJAC, B LUCZNIK et al. Iron and manganese as dopants used in the crystallization of highly resistive HVPE-GaN on native seeds. Japanese Journal of Applied Physics, SC1047(2019).

[64] R P VAUDO, X XU, A SALANT et al. Characteristics of semi-insulating, Fe-doped GaN substrates. Physica Status Solidi (A), 18(2003).

[65] J BAUR, K MAIER, M KUNZER et al. Infrared luminescence of residual iron deep level acceptors in gallium nitride (GaN) epitaxial layers. Applied Physics Letters, 857(1994).

[66] Y CORDIER, M AZIZE, N BARON et al. Subsurface Fe-doped semi-insulating GaN templates for inhibition of regrowth interface pollution in AlGaN/GaN HEMT structures. Journal of Crystal Growth, 948(2008).

[67] C C ZHENG, J Q NING, Z P WU et al. Effects of Fe doping on the strain and optical properties of GaN epilayers grown on sapphire substrates. RSC Advances, 55430(2014).

[68] D WICKRAMARATNE, J X SHEN, C E DREYER et al. Iron as a source of efficient Shockley-Read-Hall recombination in GaN. Applied Physics Letters, 162107(2016).

[70] S HEIKMAN, S KELLER, T MATES et al. Growth and characteristics of Fe-doped GaN. Journal of Crystal Growth, 248:, 513(2003).

[71] Y FANG, J YANG, Z LI et al. Optical nonlinearities and carrier dynamics in Fe doped GaN single crystal. Applied Physics Letters, 161909(2014).

[72] Y FANG, X WU, J YANG et al. Effect of Fe-doping on nonlinear optical responses and carrier trapping dynamics in GaN single crystals. Applied Physics Letters, 051901(2015).

[73] A ČĖSNA, D SÖDERSTRÖM, S MARCINKEVIČIUS et al. Carrier trapping in iron-doped GaInP. Journal of Applied Physics, 1234(1999).

[74] E RICHTER, E GRIDNEVA, M WEYERS et al. Fe-doping in hydride vapor-phase epitaxy for semi-insulating gallium nitride. Journal of Crystal Growth, 456:, 97(2016).

[75] J A FREITAS, J C CULBERTSON, E R GLASER et al. Efficient iron doping of HVPE GaN. Journal of Crystal Growth, 500:, 111(2018).

[76] M E ZVANUT, S PAUDEL, E R GLASER et al. Incorporation of carbon in free-standing HVPE-grown GaN substrates. Journal of Electronic Materials, 2226(2019).

[77] D ZHOU, Y NI, Z HE et al. Investigation of breakdown properties in the carbon doped GaN by photoluminescence analysis. Physica Status Solidi (C), 345(2016).

[78] R PIOTRZKOWSKI, M ZAJAC, E LITWIN-STASZEWSKA et al. Self-compensation of carbon in HVPE-GaN:C. Applied Physics Letters, 012106(2020).

[79] J L LYONS, A JANOTTI, C G VAN DE WALLE. Carbon impurities and the yellow luminescence in GaN. Applied Physics Letters, 152108(2010).

[80] M A RESHCHIKOV, M VOROBIOV, D O DEMCHENKO et al. Two charge states of the CN acceptor in GaN: evidence from photoluminescence. Physical Review B, 125207(2018).

[81] M E ZVANUT, S PAUDEL, U R SUNAY et al. Charge transfer process for carbon-related center in semi-insulating carbon-doped GaN. Journal of Applied Physics, 075701(2018).

[82] E RICHTER, F C BEYER, F ZIMMERMANN et al. Growth and properties of intentionally carbon-doped GaN layers. Crystal Research and Technology, 1900129(2020).

[83] P B KLEIN, S C BINARI, K IKOSSI et al. Current collapse and the role of carbon in AlGaN/GaN high electron mobility transistors grown by metalorganic vapor-phase epitaxy. Applied Physics Letters, 3527(2001).

[84] H FUJIKURA, K HAYASHI, F HORIKIRI et al. Elimination of macrostep-induced current flow nonuniformity in vertical GaN PN diode using carbon-free drift layer grown by hydride vapor phase epitaxy. Applied Physics Express, 045502(2018).

[85] Y LAI, X J LUO, X Y WANG. C-doped semi-insulating GaN grown by HVPE. Guangdong Chemical Industry, 13(2021).

[86] J L LYONS, E R GLASER, M E ZVANUT et al. Carbon complexes in highly C-doped GaN. Physical Review B, 075201(2021).