QUANTITATIVE STUDY OF THE CONTRIBUTION OF DEEP AND SHALLOW LEVELS TO THE COMPENSATION MECHANISMS IN ANNEALED INP

We have studied the effects of heat treatment under phosphorus atmosphere on the balance of electronic levels by capacitance-voltage and deep level transient spectroscopy measurements. A series of special samples was annealed under the conditions which we are normally using for the processing of nominally undoped semi-insulating (S.I.) InP. It is shown explicitly that in this annealing process the reduction of the free-carrier concentration is predominantly caused by a reduction of the net concentration of defects related to shallow levels. Furthermore, we have identified in the annealed material two defects related to electron traps with activation energies of 400 and 600 meV, which are created or incorporated during the annealing with limited concentrations of about (0.5-1) X 10(15) cm-3. On the basis of these results we conclude that for the compensation mechanism in the annealed nominally undoped S.I. InP only a concentration below 10(15) cm-3 of defects with a midgap energy level is necessary.