PN Junction with Mechanically Exfoliated Gallium Oxide and Gallium Nitride
Beta-phase gallium oxide (β-Ga2O3) is a highly stable semiconductor with an ultrawide bandgap (UWBG) of 4.6-4.9 eV, enabling applications for deep ultraviolet (DUV) and ultra-high power electronics. With a very high theoretical breakdown electric field of 8 MV/cm, saturation electron velocity of 2×107 cm/s, and Baliga’s Figure of Merit (BFOM) of 3214.1, β-Ga2O3 shows tremendous potential to perform beyond current high-power semiconductors such as GaN and SiC. In addition to the wide availability of large, low-cost, high-quality wafers of bulk β-Ga2O3, the lattice structure allows mechanical “peeling off,” or exfoliation, of layers. Since exfoliated β-Ga2O3 layers can adhere firmly to arbitrary substrates, its integration in electronic and optoelectronic devices may confer highly desirable properties, including resistance to radiation and harsh environments.
Researchers at Arizona State University have constructed the very first PN heterojunction diode between mechanically exfoliated β-Ga2O3 and p-type GaN. The mechanical exfoliation process is similar to that used for graphene and other 2D materials. Atomic force microscopy (AFM) scans of the exfoliated β-Ga2O3 flakes show very smooth surfaces with average roughness of 0.647 nm and transmission electron microscopy (TEM) scans reveal flat, clean interfaces between the β-Ga2O3 flakes and p-GaN. The device showed an approximate rectification ratio of 541.3 (V+5/V-5). Diode performance improved over the temperature range of 25°C and 200°C, leading to an unintentional donor activation energy of 135 meV. As the thickness of exfoliated β-Ga2O3 increases, ideality factors decrease as do the diode turn-on voltages, tending toward an ideal threshold voltage of 3.2 V as determined by simulation.
• Ultra-high power electronics
• High-temperature electronics
Benefits and Advantages
• Heterojunction demonstrates improved performance as temperature approaches 200°C
• Adherence of β-Ga2O3 to GaN is achieved by Van der Waals attractive forces and does not require adhesive material
• High smoothness of exfoliated β-Ga2O3 flakes result in flat, clean interfaces with GaN