| 摘要 |
PROBLEM TO BE SOLVED: To reduce loss at the time of switching of a bipolar transistor, by making the thickness and the impurity concentration of a drift layer satisfy a specified relation. SOLUTION: By making the thickness td and the impurity concentration Nd of a drift layer 201 in a semiconductor device satisfy a relation of 2.1×10<-16> (cm<-2> )<=td/Nd<=9×10<-16> (cm<-2> ), a tail current can be restrained without decreasing the current amplification factor hFE. When td/Nd<=2.1×10<-16> (cm<-2> ), the performance is sharply decreased because a carrier stored in a drift layer 201 at the time of turn-off is discharged outside a device along a flow line shown by an arrow mark Ih. As a result, a junction is biased in the forward direction by a parasitic resistance Rp in a base, and causes the tail current. When 9×10<-16> (cm<-2> )<=td/Nd, the performance is sharply decreased because the current amplification factor hFE decreases. Thereby the tail current can be decreased without deteriorating the current amplification factor hFE. |
