Patent ID: 7566641
Filing Date: 2009-07-28
Classification: C30B,H01L

Abstract:
1. A method for manufacture a gallium based material with a low etch pit density (EPD), the method comprising: performing vertical gradient freeze crystal growth using the polycrystalline gallium based compounds, including: controlling a crystallization velocity during the vertical gradient freeze crystal growth wherein the crystallization velocity is between 2 and 16 mm/hour; annealing the gallium arsenide based substrate using a single step annealing, wherein annealing the gallium arsenide based substrate further comprises controlling a heating rate during the annealing wherein the heating rate is 900 to 1050 degrees Celsius over 10 to 48 hours, as well as controlling a cooling rate during the annealing wherein the cooling rate is to room temperature in 6 to 24 hours; wherein, as a result of a combination of the vertical gradient steps, the crystallization control steps and the annealing steps, gallium based crystals are reproducibly provided having an etch pit density that is achieved without use of contact or external gas source supplied doping techniques and is less than 600 per square centimeter.