Ga2O3 Epitaxy

Ultra wideband gap (UWBG) semiconductor material gallium oxide (Ga2O3) wafer has become an ideal material for the next generation of high-power electronic devices and deep ultraviolet (DUV) solar blind photodetectors due to its unique material properties. Among the five known polycrystalline forms (α, β, γ, δ, and ε), β phase Ga2O3 with monoclinic crystal structure is the most thermally stable material. The room temperature band gap of β- Ga2O3 is between 4.5 and 4.9 eV. It also has excellent chemical, mechanical, and thermal stability at high temperatures. Compared with SiC and GaN, the conduction loss of β- Ga2O3 power devices can be reduced by an order of magnitude at the same breakdown voltage. More advantageous is that high-quality β- Ga2O3 wafers can be synthesized in large quantities through scalable and low-cost melt growth techniques, which solves the commercial limitations of current SiC and GaN based device technologies. Through homogeneous epitaxy, beta Ga2O3 epitaxy films with excellent crystal quality and controllable doping can be obtained, and this epitaxial Ga2O3 layer can be applied to vertical devices such as Schottky barrier diodes (SBDs) and field effect transistors (FETs). PAM-XIAMEN is able to supply Ga2O3 epitaxy material, please refer to the specific parameters:

1. Specification of Ga2O3 Epitaxy

2. Ga2O3 Epitaxial Growth

The extrapolation rate is related to the crystal orientation of the substrate. Homogeneous epitaxial growth of gallium oxide films on the (100) plane is the most difficult, while it’s more easier to grow on (001) and (010) planes. Therefore, (001) or (010) plane of Ga2O3 substrate is generally chosen in epitaxy and device processes.

Gallium oxide epitaxial growth techniques mainly include molecular beam epitaxy (MBE), metal organic vapor phase epitaxy (MOVPE), halide vapor phase epitaxy (HVPE), and low-pressure chemical vapor deposition (LPCVD). Among them, HVPE is a cost-effective growth technology that can produce materials with good crystal quality and fast growth rate. The HVPE growth of β – Ga2O3 thin films was carried out using gallium chloride (GaCl) and O2 as precursors at approximately 1050 ℃. N2 is used as the carrier gas. So far, the fastest growth rate of the β – Ga2O3 epitaxial layer on the (001) substrate (30) is 25 μ m/hr. For N-type doping of β – Ga2O3 thin films grown by HVPE, silicon tetrachloride (SiCl4) is used as an effective doping source. Due to the fast growth rate, the surface of the film is rough. Therefore, additional polishing procedures are required before device processing. In addition, due to the use of GaCl as the Ga source, the film exhibits the presence of impurities and defects caused by Cl.

3. Applications of Ga2O3 Epitaxial Wafers

β-Ga2O3 thin films are currently being studied for their potential applications in field effect transistors (FETs), day blind ultraviolet detectors, Schottky barrier diodes (SBDs), and gas sensing devices.

β-Ga2O3 FET: β – Ga2O3 based FET has broad application prospects as the next generation of power electronic devices and has been studied in recent years. So far, the highest breakdown voltage of β – Ga2O3 based FETs is 3.8MV/cm (45), surpassing GaN (3.3MV/cm) and SiC (2.5MV/cm).

Deep UV (DUV) day blind photodetectors: Deep UV day blind photodetectors (cutoff wavelength<280nm) have received widespread attention for their civil applications in secure communication, ozone hole monitoring, flame detection, and chemical/biological analysis. Monoclinic β – Ga2O3 is a promising candidate for deep ultraviolet sun blind photodetectors due to its ideal properties, such as a band gap of ~4.5-4.9 eV and excellent chemical, mechanical, and thermal stability.

Schottky barrier diode (SBD): Due to its predicted high breakdown electric field (Eb~6-8MV/cm) and reasonable electron mobility (µ~200-300cm2/Vs), β – Ga2O3 is expected to have a larger Baliga figure of merit (FOM) (ε µ Eb3, where ε is the relative dielectric constant) compared to SiC or GaN. So far, the highest breakdown voltage reported for field plating (FP) Schottky barrier diodes grown through HVPE based on β – Ga2O3 drift layers is~1076V.

Gas sensors: In recent years, many gas sensors prepared using Ga2O3 epitaxy and nanomaterials have been studied. The working principle of an oxygen sensor is that the conductivity of β – Ga2O3 film is inversely proportional to the oxygen partial pressure in the surrounding environment. At temperatures around 600℃, the oxygen sensitivity of Ga2O3 significantly decreases and can be used to detect reducing gases such as hydrogen.

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