In this paper, the wet chemical etching rate of AlGaN in different temperature of KOH aqueous solution was calculated and discussed. It was also found that wet chemical etching after dry etching can effectively eliminate the damage introduced by dry etching process and improve the device performance. The surface morphologies and the compositions of both sets were observed by scanning electron microscopic (SEM), atomic force microscopic (AFM) and Auger electron spectroscopy (AES). The leakage currents of visibleblind devices were compared. It is obvious that dry etching damages and devices leakage current are reduced after wet chemical etching.