A buried tungsten (W) mask structure with GaN is successfully obtained by epitaxial lateral overgrowth (ELO) technique via low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). The selectivity of GaN growth on the window region vs. the mask region is good. An underlying GaN with a striped W metal mask is easily decomposed above 500 °C by the W catalytic effect, by which radical hydrogen is reacted with GaN. It is difficult to bury the W mask because severe damage occurs in the GaN epilayer under the mask. It is found that an underlying AlGaN/GaN layer with a narrow W stripe mask width (mask/window = 2/2 μm) leads the ELO GaN layer to be free from damage, resulting in an excellent W-buried structure.

Selective area growth (SAG) and epitaxial lateral overgrowth (ELO) of GaN using tungsten (W) mask by metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) have been studied. The selectivity of the GaN growth on the W mask as well as the SiO2 mask is excellent for both MOVPE and HVPE. The ELO-GaN layers are successfully obtained by HVPE on the stripe patterns along the <1 00> crystal axis with the W mask as well as the SiO2 mask. There are no voids between the SiO2 mask and the overgrown GaN layer, while there are triangular voids between the W mask and the overgrown layer. The surface of the ELO-GaN layer is quite uniform for both mask materials. In the case of MOVPE, the structures of ELO layers on the W mask are the same as those on the SiO2 mask for the <11 0> and <1 00> stripe patterns. No voids are observed between the W or SiO2 mask and the overgrown GaN layer by using MOVPE.

A buried tungsten (W) mask structure with GaN is successfully obtained by epitaxial lateral overgrowth (ELO) technique via low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). The selectivity of GaN growth on the window region vs. the mask region is good. An underlying GaN with a striped W metal mask is easily decomposed above 500 °C by the W catalytic effect, by which radical hydrogen is reacted with GaN. It is difficult to bury the W mask because severe damage occurs in the GaN epilayer under the mask. It is found that an underlying AlGaN/GaN layer with a narrow W stripe mask width (mask/window = 2/2 νm) leads the ELO GaN layer to be free from damage, resulting in an excellent W-buried structure.

Selective area growth (SAG) and epitaxial lateral overgrowth (ELO) of GaN using tungsten (W) mask by metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) have been studied. The selectivity of the GaN growth on the W mask as well as the SiO2 mask is excellent for both MOVPE and HVPE. The ELO-GaN layers are successfully obtained by HVPE on the stripe patterns along the <1100> crystal axis with the W mask as well as the SiO2 mask. There are no voids between the SiO2 mask and the overgrown GaN layer, while there are triangular voids between the W mask and the overgrown layer. The surface of the ELO-GaN layer is quite uniform for both mask materials. In the case of MOVPE, the structures of ELO layers on the W mask are the same as those on the SiO2 mask for the <1120> and <1100> stripe patterns. No voids are observed between the W or SiO2 mask and the overgrown GaN layer by using MOVPE.

We have succeeded in making high resistive AlxGa1−xAs by oxygen doping (AlxGa1−xAs:O) and applying them to buffer layer for power metal-semiconductor field effect transistor (MESFET). Samples of Al0.3Ga0.7As:O were prepared by metalorganic vapor phase epitaxy (MOVPE). Oxygen-related levels in A10.3Ga0.7As:O were investigated by applying isothermal capacitance transient spectroscopy (107S) to MIS (Al/Al0.3Ga0.7As:O/n-GaAs) diodes. A breakdown voltage and a two terminal gate breakdown voltage of the MESFET with the Al0.3Ga0.7As:O buffer layer became higher as increasing in the intensity of oxygen related peak in the ICTS spectra. These results indicate that the electrically active oxygen in the Al1−xGa1−xAs:O is an important factor for the device characteristics.