| 摘要 |
PURPOSE:To obtain an epitaxial wafer for GaAlAs based LED in which the emission output is not decreased even if the mixed crystal ratio y2 on the surface of an n-type clad layer is set at 0.55 or less and high emission output is realized while enhancing the reliability. CONSTITUTION:A p-type Ga1-xAlxAs active layer and an n-type Ga1-yAlyAs clad layer are formed on a p-type GaAs substrate at a mixed crystal ratio required for a desired emission wavelength thus producing an epitaxial wafer of single or double hetero structure. Each layer is grown by gradual cooling method and the gradual cooling rate RN is set in the range of 0.1<=RN<=0.5 deg.C/min which is slower than conventional rate when the n-type clad layer is grown. Assuming the initial mixed crystal ratio of the n-type Ga1-yAlyAs clad layer is y1, the surface mixed crystal ratio is y2, and the mixed crystal ratio of the p-type Ga1-xAlxAs active layer is x, the n-type clad,layer is grown to satisfy the following three conditions, i.e., 0.55<=y1<0.70, x<y2<=0.55, and 0.75<y2/y1<0.9, simultaneously by regulating the growth starting temperature and the charging quantity of Al. |
