| 摘要 |
PURPOSE:To obtain an avalanche photo diode of low noise and moreover having broad wavelength band sensitivity by a method wherein a first layer having the single conductive type, and consisting of the mixed crystal of the III-V group semiconductors having nearly equal forbidden band width and spin separating energy is put between a second layer and a third layer having forbidden band widths larger than the first layer, and moreover having the mutually different conductive types. CONSTITUTION:A depletion layer is constructed of Ga1-xAlxSb layers 1-3 of three kinds having the different values of (x), and the layer 1 is made as the incidence side. The values of (x) of the respective layers are made respectively as x1, x0, x2. The layer 2 is formed of a material shown by EGapprox.=DELTA0 making as x0approx.=0.052, and the layer 1 and the layer 3 on both the sides thereof are formed of the materials of more larger forbidden band widths EG making as x1>x0, x2>= x0. When a reversely directional voltage is applied to the diode thereof, an electric field becomes to the maximum at the layer 2, and moreover the fact that EG of the layer 2 is the minimum is added thereto, and avalanche breakdown is generated almost only in the layer 2. When thickness of the layer 2 is made sufficiently thick, light is nearly absorbed by the layer 1 and the layer 2, wavelength sensitivity is nearly decided by forbidden band widths EG of the layers 1, 2, and short wavelength sensitivities according to both the layer 1 and the layer 2 are added moreover to long wavelength sensitivity at the layer 2. |
