Simultaneous analysis of current-voltage and capacitance-voltage characteristics of metal-insulator-semiconductor diodes with a high mid-gap trap density

We present an improved method to analyze simultaneously the current-voltage and capacitance-voltage characteristics of metal-insulator-semiconductor ( MIS) diodes. We use the method to study the effect of Zn doping concentrati on on the current transport in Au MIS contacts fabricated on In0.21Ga0.79As layers grown by metalorganic vapor phase epitaxy on highly doped GaAs subs trates. At room temperature and for low reverse bias voltage, the generatio n/recombination process via mid-gap traps is the only dominant mechanism in these MIS diodes. For high reverse bias, both this mechanism and thermioni c-field emission control current transport. The generation/recombination cu rrent observed is due to donor type mid-gap traps whose density shows an al most linear dependence with Zn concentration. The value of the barrier heig ht at zero bias and at room temperature (phi(b0) = 0.73 V +/- 12%) is indep endent of the Zn concentration. For the procedure used to prepare the In0.2 1Ga0.79As: Zn surfaces, the thickness of the oxide layer and the transmissi on coefficient of holes across this layer depend on the Zn doping concentra tion in the range 7 x 10(14) less than or equal to N-A less than or equal t o 5 x 10(18) cm(-3). Zn doping seems to inhibit the formation of the uninte ntional native oxide on the surface of In0.21Ga0.79As epilayers. (C) 1999 A merican Institute of Physics. [S0021-8979(99)02508-6].