| 摘要 |
PURPOSE:To much effectively perform a light coupling by forming a structure that the energy gap of a collector layer is reduced smaller than that of a base layer by altering the compositions of the collector and base layers. CONSTITUTION:The composition of a crystal is set to become the relationship of Eg4>=Eg3>Eg2 in the relationship between the energy gaps Eg2 and Eg4 among a collector layer 2, a base layer 3 and an emitter layer 4. In case of Eg4>=Eg3, the improvements in the current injection efficiency by wide gap emitter and light input/output efficiency of upper emitter layer 4 side are performed. Since Eg3>Eg2 is satisfied, the high sensitivity photoreceiving wave length band of a transistor is substantially lambda4(=K/Eg4)<lambda3(=K/Eg3)<lambda2(=K/Eg2) (where K is constant, approx. 1240nm/eV). Accordingly, there are characteristics having high sensitivity photoreceiving wavelength band from the wavelength of emitting light to longer wavelength for the external incident light from upper and lower and lateral directions. |
