| 摘要 |
PURPOSE:To obtain the impurities having an optional density distribution in a semiconductor by a method wherein the surface of the semiconductor is covered by an absorbing material such as metal and the like, an aperture is made and a nuclear reaction is generated by irradiating a radiant ray. CONSTITUTION:The whole exposed surface of the semiconductor substrate 1, made of P type GaAs and the like, is covered by an absorbing material 2 consists of a Gd metal layer by performing a sputtering evaporation, and a pattern of slit-type 3 is made corresponding to the prescribed region. Then the substrate is placed in a nuclear reactor, a radiant ray 4 is irradiated by having a thermal neutron density of approximately 4X10<13> piece/cm<2>-second and the exposed region in the slit 3 of the substrate 1 is converted to an N type layer 5 having a carrier density of 1X10<17>/cm<2>. Thus a layer 5 having a steep carrier density distribution can be obtained without changing too much of the resistance value of the substrate 1. In this constitution, when a more steep density distribution is reguired, the radial ray 4 is formed into a beam-typed radial ray flux using a hollow collimator 6. Also an optional density can be obtained by selecting a desired thermal neutron density. |
