3:30 PM - 3:45 PM
▲ [7p-C17-8] Morphological and Electrical Properties of β-Ga2O3 (010) Layers Grown by Plasma-Assisted Molecular Beam Epitaxy
Keywords:Ga2O3, PAMBE
This work presents morphological and electrical properties of β-Ga2O3 (010) layers grown by plasma-assisted molecular beam epitaxy (PAMBE). We also investigated effects of O2 plasma treatment on Ga2O3 epilayer/substrate interfaces.
Ga2O3 layers with a thickness of 700 nm were grown on n+-Ga2O3 (010) substrates by PAMBE. The nominal growth rate and substrate temperature were set at 350 nm/h and 620ºC, respectively. To investigate the effects of O2 plasma treatment for removing Si contamination on the substrate surface, we performed two different surface treatment sequences prior to the MBE growth. For one sample, the Ga2O3 substrate underwent only annealing at 700ºC for 30 min in a high vacuum growth chamber (~5×10-10 Torr). For the other one, the substrate surface was irradiated by oxygen radicals/ions during the annealing process at 700ºC.
The sample without the plasma treatment showed an atomically flat surface with a root-mean-square (RMS) roughness of 0.8 nm. On the other hand, some hillocks were formed on the surface of the Ga2O3 layer grown after the O2 plasma treatment with a resulting surface RMS roughness of 2.8 nm.
To investigate electrical properties of the unintentionally doped (UID) Ga2O3 epilayers, vertical Schottky barrier diode (SBD) structures were fabricated using the two epitaxial wafers. The depth profiles of net donor concentrations (Nd–Na) obtained from capacitance–voltage (C–V) characteristics revealed that charges with a density of about 6×1017 cm-3 existed at the epilayer/substrate interfaces for both samples, suggesting that the pre-growth plasma treatment didn’t work effectively in diminishing Si contamination on the substrate. From forward current density–voltage characteristics, residual electron concentrations in the UID Ga2O3 thin films grown without and with the plasma treatment were estimated to be 2.3×107 and 3.1×108 cm-3, respectively.
Ga2O3 layers with a thickness of 700 nm were grown on n+-Ga2O3 (010) substrates by PAMBE. The nominal growth rate and substrate temperature were set at 350 nm/h and 620ºC, respectively. To investigate the effects of O2 plasma treatment for removing Si contamination on the substrate surface, we performed two different surface treatment sequences prior to the MBE growth. For one sample, the Ga2O3 substrate underwent only annealing at 700ºC for 30 min in a high vacuum growth chamber (~5×10-10 Torr). For the other one, the substrate surface was irradiated by oxygen radicals/ions during the annealing process at 700ºC.
The sample without the plasma treatment showed an atomically flat surface with a root-mean-square (RMS) roughness of 0.8 nm. On the other hand, some hillocks were formed on the surface of the Ga2O3 layer grown after the O2 plasma treatment with a resulting surface RMS roughness of 2.8 nm.
To investigate electrical properties of the unintentionally doped (UID) Ga2O3 epilayers, vertical Schottky barrier diode (SBD) structures were fabricated using the two epitaxial wafers. The depth profiles of net donor concentrations (Nd–Na) obtained from capacitance–voltage (C–V) characteristics revealed that charges with a density of about 6×1017 cm-3 existed at the epilayer/substrate interfaces for both samples, suggesting that the pre-growth plasma treatment didn’t work effectively in diminishing Si contamination on the substrate. From forward current density–voltage characteristics, residual electron concentrations in the UID Ga2O3 thin films grown without and with the plasma treatment were estimated to be 2.3×107 and 3.1×108 cm-3, respectively.