gaas surface the structure of the ga 2 o 3 layer is dependent on the current density at the current densities higher than 1 ma cm 2 the crystalline u03b2 ga 2 o 3 forms at the interface which can increase the density of the interface states it should be noted that the oxide bulk properties can be improved by the application of higher current density during the oxidation the reason is that the as 2 o 3 forms and becomes a part of the oxide before leaching out the carrier exchange between the interface states and the semiconductor by tunneling can be responsible for the long time constant involved on the order of five minutes in the transition 34 1 34 fig5 c this time constant is measured by interrupting the secondary light while monitoring the tav change between equilibrium values the relative maximum observed around 1 25 ev in fig2 b c and d can be due to a donor band above the valence band anodic oxidation of semiconductors has been used successfully to grow a good quality oxide on semiconductor surfaces having better characteristics than thermally grown oxides the presently disclosed new means of growing a selective oxide is very useful in fabrication processes due to the elimination of the oxide etching step more particularly the oxide can be grown in the form of the desired pattern during the growing process an embodiment of the invention for carrying out such process is shown in fig6 the apparatus 10 comprises a non conductive container 12 for containing electrolyte 14 counter electrode 16 and semiconductor 18 the actual electrolytic process is driven by electrical driver unit 20 where the negative side of driver 20 is coupled to electrode 16 and the positive.