Enhancing the perfection of bulk (1 0 0) β-Ga2O3 crystals grown by Czochralski method

Abstract

Gallium Oxide is a prospective ultra-wide band-gap semiconductor for high-voltage electronics. Bulk β-Ga2O3 crystals can be utilized as substrates for device structures. The biggest challenge encountered is to grow low defect density wafers with high crystal perfection.In this work a boule with a diameter of about 20 mm and a height of 20 mm was grown by Czochralski method. The separate plates with dimensions of approx. (10 × 5 × 3)mm3 were cleaved out from the crystal along the (100) cleavage planes.XRD investigation demonstrated that the crystal is a monoclinic single-phase structure which is characterized by broad rocking curves. The etch pits density revealed by selective wet etching appeared to be high and was estimated as 2 · 107 cm−2. The series of post-growth heat treatments was applied to eliminate these drawbacks. Annealing at 1100 °C during 5 h had the most effect on the crystal structure. Namely, its coherent-domain-size value increased over 400 nm, domain misorientation dropped below the arcminute. The crystal developed higher stoichiometry and higher crystalline perfection. Annealing at the same temperature, but for duration of 11 h dramatically worsen all the parameters of the crystal in combination with its fragmentation in smaller-sized domains. The etch pits density finally decreased 40-fold and took a value of 5 · 105 cm−2.