| 摘要 |
PURPOSE:To obtain a high performance transistor by hetero epitaxially growing semiconductor layers of three types having the sum of forbidden band width Eg in the prescribed relationship in an electron affinity X range, thereby eliminating a metal base. CONSTITUTION:When the X1 of an emitter 21 is selected to smaller value than the X2 of a base 22 and X3 of a collector 23, an emitter barrier becomes X2-X1. As an example of an N type device, the emitter is composed of an N type Al0.3Ga0.7As and a high density electrode layer 211, electron density is 3X10<21>/ m<3>, 1X10<22>/m<3> in the portion contacted with the base, a tunnel effect is prevented, the thickness is set to 3- 50nm, thereby holding the emitter and base withstand voltage. No-additive GaAs is intentionally used for the base 22, and the layer 211 is doped with 1X10<22>/m<3> and ohmically contacted with metal electrode. The collector 23 is composed of I type or N type Al0.2Ga0.8As and a high density layer 231 of the same composition, a layer which has a doping amount of 1X10<22>/m<3> or less and 5-10<3>nm of thickness is provided on the portion contacted with the base to hole the collector withstand voltage. According to this construction, the base layer can be reduced in high accuracy, the defect of a metal base transistor can be eliminated, and a device having various advantages can be obtained. |
