Bandgap Tailoring of Monoclinic Single‐Phase β‐(Al_xGa_1−x)₂O₃ (0 ≤ x ≤ 0.65) Thin Film by Annealing β‐Ga₂O₃/Al₂O₃ Heterojunction at High Temperatures

Abstract

Recently, β-Ga 2 O 3 has attracted extensive attention because of its ultrawide bandgap (%4.8 eV), [1,2] high theoretical breakdown electric field (E br ) (8 MV cm À1 ), [3,4] and higher Baliga figure of merit (BFOM) compared with GaN and SiC. The highly mature bulk growth and thin film deposition techniques [5][6][7] make both homo- [8][9][10] and heteroepitaxial [11,12] growth of Ga 2 O 3 thin films with controllable doping possible, [13][14][15][16] which is important for practical applications such as power switches, [17,18] high-efficiency devices, [19] and deep-UV photodetectors. [20,21] To develop and optimize modern electronic and optoelectronic devices with great flexibility, energy band engineering is necessary for designing and preparing barrier layers, which show better carrier confinement with larger band offsets in device structures. [22] It has been demonstrated that the bandgap of β-(Al x Ga 1Àx ) 2 O 3 depends on the Al composition (x), and increases with it. [23] Many works in the literature report the growth of β-(Al x Ga 1Àx ) 2 O 3 thin films using molecular beam epitaxy (MBE), [24][25][26] metal organic chemical vapor deposition (MOCVD), [27] pulsed laser deposition (PLD), [28] sputtering [29] and solution combustion synthesis, [30] etc., and studies on the Al incorporation effect on the surface morphology and crystalline quality, which are summarized in Table 1. β-(Al x Ga 1Àx ) 2 O 3 epitaxial film by MOCVD and MBE is mainly used for highpower electronic applications. For instance, by constructing a β-(Al x Ga 1Àx ) 2 O 3 /β-Ga 2 O 3 heterojunction with a Si delta-doped layer in β-(Al x Ga 1-x ) 2 O 3 to prepare a modulated doped field effect

The Heteroepitaxy of Thick β-Ga2O3 Film on Sapphire Substrate with a β-(AlxGa1−x)2O3 Intermediate Buffer Layer

“…The O1s peak energy was 530.8 eV, while the initial inelastic losses were 536.8 eV. The bandgap of β -(Al x Ga 1−x ) 2 O 3 film extracted from the O1s spectra was approximately 6.0 ± 0.1 eV, which is consistent with the bandgap energy estimated by absorption spectra in previous literature [ 30 ]. The impurity in the β -(AlxGa1-x)2O3 film was investigated using time-of-flight secondary ion mass spectrometry (SIMS, IONTOF 5).…”

High-quality β-(AlxGa1−x)2O3 thin films on sapphire substrates by face-to-face annealing

“…[23][24][25] Interestingly, a peak appears at around 240 cm −1 when the annealing temperature is raised to 1300 °C, which is consistent with the previously reported outcomes for β-(Al x Ga 1−x ) 2 O 3 . 26 Moreover, the location of this peak gradually shifts to a higher wavenumber with increasing the annealing time at 1300 °C and its intensity also increases simultaneously, which should result from the increased Al content in β-(Al x Ga 1−x ) 2 O 3 . 26,27 Likewise, another vibrational peak at around 830 cm −1 should be related to the stretching and bending of the shortest Ga-O (A 10 g ) bonds.…”

“…26 Moreover, the location of this peak gradually shifts to a higher wavenumber with increasing the annealing time at 1300 °C and its intensity also increases simultaneously, which should result from the increased Al content in β-(Al x Ga 1−x ) 2 O 3 . 26,27 Likewise, another vibrational peak at around 830 cm −1 should be related to the stretching and bending of the shortest Ga-O (A 10 g ) bonds. 28 The Ga-O bonds are replaced by Al-O bonds, leading to a reduction in the stretching and twisting stress of the Ga-O bonds.…”

Improved Properties of Post-Deposition Annealed Ga2O3/SiC and Ga2O3/Al2O3/SiC Back-Gate Transistors Fabricated by Radio Frequency Sputtering

“…Meanwhile, in the Ga2O3/Al2O3/SiC structures (Figure 2b,d), Al, O, Si, and C atoms had not diffused into the opposite SiC substrates or Al2O3 films. However, gradient changes of Ga and Al atomic concentrations at the Ga2O3/Al2O3 interface indicate the interdiffusion of Ga and Al atoms [23,24]. Therefore, (AlxGa1−x)2O3 ternary compounds at the Ga2O3/Al2O3 interfaces were formed during the annealing of the devices.…”