| 摘要 |
PURPOSE:To improve a wave tail, to make high the speed of operation and further to furnish PC of high sensitivity, by forming a light-receiving semiconductor layer on a half-insulative semiconductor substrate and by forming the light- receiving semiconductor layer of a P-type semiconductor layer. CONSTITUTION:When electrodes 13 and 14 made up of Ti/Pt/Au are space at 10mum from each other, a time required for electrons generated by irradiation of light to go across the space is 40pS. This value is smaller by one figure than the one in the case of an N-type, and thus a fall time is shortened. On the other hand, thermal noise <it<2>> of PC is expressed by <it<2>>=4kTB/RD, where (k) denotes a Boltzmann constant, T an absolute temperature, B a band and RD the resistance of PC. The electrodes of PC are comb-shaped to increase the efficiency of light reception. While the thermal noise of an avalanche photodiode can be expressed in the same way, a resistance of 50OMEGA or above is connected as RD generally so as to secure matching with an external circuit when APD is used. Accordingly, while the thermal noise in a light-receiving semiconductor layer of an N-type is larger than that in APD, this can be avoided by forming the layer of a P-type one. |
