| 摘要 |
PURPOSE:To realize a base region in high concentration under the state in which high mobility is maintained, and to obtain the base region having resistance extremely lower than conventional devices by using semiconductor layers, in which semiconductors, to which an impurity is doped to a high degree and which have large forbidden band width, and semiconductors not doped intentionally are superposed alternately and to which the impurity is modulation-doped, as the base region. CONSTITUTION:P type GaAs 5 and AlX2Ga1-X2As 6 having different borbidden band width are laminated as the structure of the conduction band of a base region. When x1>=0.3 holds as N-AlX1Ga1-X1As 4, the thickness d1 of P type GaAs 5 extends over 10<d1<300Angstrom , 0.1<=x2<=0.3 holds as P type AlX2Ga1-X2As 6, thickness thereof d2 extends over 10<d2<300Angstrom and P type impurity concentration is brought to 0.5-5X10<19>cm<-8>, a hetero-junction bipolar transistor having low base resistance and a high current amplification factor of 100 or more can be realized. Accordingly, base resistance can be lowered up to the limit or more of the reduction of the base resistance of conventional hetero-junction bipolar transistors, thus realizing an ultraspeed transistor more excellent than conventional devices. |
