Comparative Studies of c- and m-Plane AlN Seeds Grown by Physical Vapor Transport

Abstract

The ultra-wide bandgap semiconductor AlN has attracted a great deal of attention owing to its wide application potential in the field of electronics and optoelectronic devices. In this report, based on the mechanism of the physical vapor transport (PVT) growth of AlN crystal, the c- and m-plane AlN seed crystals were prepared simultaneously through special temperature field design. It is proved that AlN crystals with different orientations can be obtained at the same temperature field. The structure parameter of AlN crystal was obtained through the characteristic evaluations. In detail, XPS was used to analyze the chemical states and bonding states of the surface of seed crystals. The content of oxygen varied along with distinct orientations. Raman spectrum documented a small level of compressive stress on these crystal seeds. Tested results confirmed that the prepared AlN crystal seeds had high quality.

The stacking fault annihilation in a-plane AlN during high-temperature annealing

“…4 (670.8 and 657.4 cm −1 ) are the phonon frequencies of E 1 (TO) and E 2 (high) for strain-free AlN, respectively. [34][35][36] Here, we extracted the E 1 (TO) and E 2 (high) peak positions of all the a-AlN samples from the Raman curves in Fig. 4 1 and Table 1, it can be found that the blue-shift of the Raman peaks increases with the decreasing BSFD, which means that the compressive stress was accumulated with the decrease in BSFD.…”

“…4 (670.8 and 657.4 cm −1 ) are the phonon frequencies of E 1 (TO) and E 2 (high) for strain-free AlN, respectively. 34–36 Here, we extracted the E 1 (TO) and E 2 (high) peak positions of all the a -AlN samples from the Raman curves in Fig. 4(a) and (c), and the results are summarized in Fig.…”

Optimization of the process parameters for the AlN crystal growth in the PVT method through an improved numerical simulation considering partial pressure of gas phases

“…Various methods have been tried to prepare AlN single crystals, including hydride vapor phase epitaxy (HVPE), 11 the ammonothermal method, 12 molecular beam epitaxy (MBE), 13 metal-organic chemical vapor deposition (MOCVD), 14 and physical vapor phase transport (PVT). 15,16 Among them, PVT is the most successful method for preparing high-quality and large-size AlN single crystals. However, the PVT method still faces many challenges in experiments, such as a limited growth environment, high growth temperature of up to 2000-2300 °C, long growth period, and high degree of stability and control accuracy in the temperature field.…”