Increase in the growth rate of GaN crystals by using gaseous methane in the Na flux method

Abstract

In the growth of GaN using the Na flux method, the addition of graphite to the flux enables us to suppress the formation of GaN polycrystals generated around the gas–liquid interface and to increase the growth rate of GaN on a seed. To increase the growth rate further, high nitrogen pressure conditions are used. However, polycrystals are easily generated even if graphite is added. In this study, we first applied methane gas as a carbon source in order to increase the carbon concentration around the gas–liquid interface and to suppress polycrystal formation, even at high nitrogen pressures. As a result, polycrystal formation was suppressed completely at nitrogen pressures as high as 5.0 MPa, by using methane gas, resulting in the highest growth rate of more than 60 µm/h in the c-direction among the crystals grown by the Na flux method.