JPS649656A - Bipolar transistor - Google Patents

Abstract

PURPOSE:To accelerate an NPN type transistor whose base resistance is several times smaller compared with conventional ones subject to the same base layer thickness and P-type impurity concentration of the base by providing the transistor with a strain superlattice structured base layer. CONSTITUTION:A strain superlattice is led in a base layer 2. For example, In0.52Al0.48As is used for an emitter 1 and a collector 3 as semiconductor material while In0.53+xGa0.47-xAs and In0.53-xGa0.47+xAs (x=0.15) are used for a base 2 and respective elements 1, 2 and 3 are alternately laminated in thickness of 200Angstrom to dope P type impurity such as berillium etc. Here, the compressive force is given to an In0.35+xGa0.47-xAs layer to increase the hole mobility assuming x=0.15 instead of x=0 up to four times at the room temperature and ten times at 77K. Thus, subject to the same base layer thickness and the P type impurity concentration, the base resistance can be reduced down to 1/2 at the room temperature and 1/5 at 77K compared with the conventional base resistance enabling high speed transistors to be manufactured.