voltage v th has been defined by a gate voltage with which when a voltage of 2 v is applied across the source and drain electrodes a drain current becomes 5 u03bca for a gate width of 10 u03bcm to the end of bringing the lattice distortions in the wafer u03b4d d o into the range limited by eq 1 or eq 3 a gaas single crystal of high purity having an impurity concentration less than 1 u00d7 10 16 cm u2212 3 was produced by the pulling method the gaas single crystal of the present invention however is not restricted to the pulling method the method of crystal growth will be described with reference to fig4 the pulling method itself may be a well known technique which is reported in for example u2018 semi insulating iii v compound crystal technology u2019 by takatoshi nakanishi proceedings of the institute of electrical communication 66 1983 p 503 by controlling the conditions of the crystal growth lattice constants are controlled the measurement of the lattice constants suffices with for example well known x ray diffraction based on a well known double crystal method using is a schematic sectional view which double x ray beams fig4 is a schematic sectional view which shows the concept of the so called lec liquid encapsulated czochralski method a pbn pyrolitic boron nitride crucible 16 is charged with ga and as of raw materials which are brought into a.