Group‐III Sesquioxides: Growth, Physical Properties and Devices

Abstract

The group‐III sesquioxides possess material properties that render them interesting for applications such as high‐power rectifiers and transistors, solar‐blind UV detectors and inter‐sub‐band infrared detectors. Technology for growing large, single‐crystalline bulk material and for wafer fabrication exists, enabling homoepitaxial growth of thin films with high crystalline quality. The bandgap can be tuned in an energy range from about 4 to 8 eV for the ternary alloys and allows growth of heterostructures with large band offset. Here, past results and recent investigations on the growth, the material properties, contact fabrication and the alloying of group‐III sesquioxides are reviewed, and an overview on demonstrator devices is provided.

Optimizing the Stoichiometry of Ga2O3 Grown by RF‐Magnetron Sputter Deposition by Correlating Optical Properties and Growth Parameters

“…The material and its processing offer various degrees of freedom for optimizing its structure for a specific application. Five different crystalline phases of Ga 2 O 3 , denoted as α, β, γ, δ, and ϵ phase, are known to date . The β‐phase has the highest thermal and chemical stability among those five phases .…”

Ohmic contacts on n-type β-Ga2O3 using AZO/Ti/Au

“…There is significant promise in β-Ga 2 O 3 for use in electronics for extreme environments (high temperature, high radiation and high voltage switching) [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and for solar blind UV detection. 16 Ga 2 O 3 is suited to these applications because of its wide bandgap, ∼4.8 eV and high theoretical critical field strength ∼8 MV/cm (experimental values have reached 3.8 MV/cm).…”

“…13 Ga 2 O 3 bulk and epitaxial crystals can be grown by many methods including Czochralski, edge-defined film-fed growth (EFG), Verneuil, float-zone, molecular beam epitaxy (MBE), halide vapor phase epitaxy growth (HVPE), with excellent control of quality and n-type conductivity. 1,2,14,15,17 The β-phase of Ga 2 O 3 has a monoclinic structure and is the most commonly studied of the different polymorphs. 1,2,[18][19][20][21] Excellent results for β-Ga 2 O 3 -based power rectifiers, field effect transistors (FETs) and metal-oxide FETs (MOSFETs) have been reported, 2,4-13 along with solar blind photodetectors.…”

“…1,2,14,15,17 The β-phase of Ga 2 O 3 has a monoclinic structure and is the most commonly studied of the different polymorphs. 1,2,[18][19][20][21] Excellent results for β-Ga 2 O 3 -based power rectifiers, field effect transistors (FETs) and metal-oxide FETs (MOSFETs) have been reported, 2,4-13 along with solar blind photodetectors. 1,2,16 In all cases, these devices would benefit from an improved low resistance Ohmic contacting process that requires only moderate annealing temperatures.…”

“…1,2,[18][19][20][21] Excellent results for β-Ga 2 O 3 -based power rectifiers, field effect transistors (FETs) and metal-oxide FETs (MOSFETs) have been reported, 2,4-13 along with solar blind photodetectors. 1,2,16 In all cases, these devices would benefit from an improved low resistance Ohmic contacting process that requires only moderate annealing temperatures. 4,8 To date, the lowest specific contact resistance of ∼4.6×10 -6 Ω-cm 2 was reported for Ti/Au contacts on n-Ga 2 O 3 epitaxial layers with Si implanted and annealed at 925 • C followed by dry etching, metal deposition and annealing at 470 • C. 21 Yao et al explored nine different metals with Au capping layers to form Ohmic contact on Ga 2 O 3 , with many current-voltage ( I-V) results being pseudo-Ohmic, and the best results obtained using Ti/Au.…”