Patent ID: 7387989

Claim:
A cleaning method of an Al x Ga y In 1-x-y N substrate, wherein 0<x≦1, 0≦y≦1, x+y≦1, said Al x Ga y In 1-x-y N substrate is soaked in a cleaning solution made of one selected from the group consisting of an ammonia water, an ammonia hydroxide/hydrogen peroxide mixture and an organoalkali aqueous solution while being subjected to ultrasound, whereby particles having a grain size of at least 0.2 μm on a surface of said Al x Ga y In 1-x-y N substrate are made to be at most 20 in number when a diameter of said Al x Ga y In 1-x-y N substrate is two inches, as said cleaning solution, one of an ammonia water having an ammonia concentration of at least 0.5 weight percent, an ammonia hydroxide/hydrogen peroxide mixture having a hydrogen peroxide solution concentration of at least 0.1 weight percent and an ammonia concentration of at least 0.1 weight percent, and an organoalkali aqueous solution having an organoalkali concentration of at least 0.5 weight percent is used, said organoalkali aqueous solution is organoalkali dissolved in water, said organoalkali being one of tetramethylammonium hydroxide and 2-hydroxyethyl trimethylammonium hydroxide, and a soaking time of said Al x Ga y In 1-x-y N substrate is at least 30 seconds.