Epitaxial single‐crystal of GaSe epilayers grown on a c‐sapphire substrate by molecular beam epitaxy

Abstract

In this study, hetero-epitaxy of GaSe epilayers on a c-sapphire substrate achieved using molecular beam epitaxy was demonstrated. The GaSe epitaxial growth was monitored using in situ reflection high-energy electron diffraction (RHEED). Streak RHEED patterns showed a flat and highly crystalline situation. Furthermore, two RHEED patterns were observed after 15 min of growth, and they were correlated with the m-axis and a-axis of hexagonal GaSe. The single crystal of GaSe was verified using X-ray diffraction and high-resolution cross-section transmission electron microscopy. The full width at half-maximum of (0002) in the XRD rocking-curve spectrum of GaSe epilayer is obtain around 207 arcsec, which is the smallest value observed to date. The epitaxial growth of GaSe demonstrated the feasibility of growing large-area epilayers.

Atomistic study of GaSe/Ge(111) interface formed through van der Waals epitaxy

“…Since the positions of the new streaks compared with those of the Ge(111) streaks are consistent with the lattice constant difference between GaSe(0001) and Ge(111), which are 3.75 Å and 4.00 Å, respectively, it indicates that the GaSe thin film is growing on Ge(111) with the epitaxial relationship GaSe(0001) // Ge (111) and GaSe [11][12][13][14][15][16][17][18][19][20] // Ge [1][2][3][4][5][6][7][8][9][10]. As the growth proceeds, the Ge(111)-(1 × 1) streaks fade out and, in contrast, the GaSe(0001)-(1 × 1) streaks gradually become clearer and sharper ( Figure 1D).…”

“…We investigated the growth of GaSe on Ge(111) by MBE and determined the atomistic structure of the thin film near the interface using HAADF-STEM and EELS. It was revealed that GaSe thin films can be grown on Ge(111) with GaSe(0001) // Ge(111) and GaSe [11][12][13][14][15][16][17][18][19][20] // Ge [1][2][3][4][5][6][7][8][9][10], and the Ge(111) surface is terminated by a half GaSe monolayer, on which the GaSe thin film is grown through vdWE. The grown layers adopt predominantly the expected wurtzite-like structure but monolayers with a zinc blende-like structure are locally observed near the film-substrate interface, which has not been reported previously.…”

“…No growth temperature dependence was observed up to 525°C, while at 550°C, only the Ge(111)-(1 × 1) pattern is visible during the growth which suggests that at this substrate temperature, the growth of GaSe does not occur. GaSe [11][12][13][14][15][16][17][18][19][20] // Ge [1][2][3][4][5][6][7][8][9][10] between the thin film and the substrate (Figure 2A). In addition to the expected ε-type stacking which is the most thermodynamically stable one 17 (Figure 2B), we found that other stacking types of GaSe monolayers can be formed near the interface.…”

“…So far, GaSe has been used in metal‐oxide‐semiconductor field‐effect transistors and photodetectors . By vdWE, the growth of GaSe has been reported on many substrates including WS 2 , MoSe 2 , Si(111), Si(110), Si(100), GaAs(111), GaAs(110), GaAs(100), c‐sapphire, and GaN(0001) …”

“…6 So far, GaSe has been used in metal-oxide-semiconductor field-effect transistors 7 and photodetectors. 5,8 By vdWE, the growth of GaSe has been reported on many substrates including WS 2 , 9 MoSe 2 , 10 Si(111), Si(110), Si(100), 11 GaAs(111), 12,13 GaAs(110), 14 GaAs(100), 13 c-sapphire, 15 and GaN(0001). 16 In the present study, we investigated the growth of GaSe on Ge(111) by molecular beam epitaxy (MBE).…”