| 摘要 |
PURPOSE:To obtain an APD of low noise wherein the rate of ionization is increased sufficiently by a method wherein the first semiconductor layer having a thickness less than a specific value and the second conductor layer having a forbidden band width larger than the thickness and a thickness less than a specific value are laminated alternately by double layer and more respectively. CONSTITUTION:When the thicknesses of GaAs layers 1 and Al0.5Ca0.5As layers 2 which have forbidden band widths Eg1 and Eg2 respectively and are laminated alternately are 300Angstrom or less and 200Angstrom or less respectively, the thickness of each layer 1 and 2 becomes approximately equal to the de Broglie wavelength of the electron. Electrons concentrated to a GaAs potential well layer 1 come to permeate through the Al0.5Ga0.5As layer 2 by tunnel effect, and accordingly quantized electron energy bands 3 and 4 are formed over each layer 1 and 2. The band doscontinuity on the side of a valence band is sufficiently small, and the interval of the energy band of formed holes is very small, therefore the interval can be approximated to the valence band of a bulk. Besides, this constitution makes the rate of electron ionization become much smaller than the rate of hole ionization. |
