Conversion Tunneling in Non-Ideal Schottky Barriers: Virtual Resonance Manifestation and Interface States Influence
- PDF / 348,039 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 108 Downloads / 212 Views
ABSTRACT We have investigated experimentally and theoretically the elastic conversion tunneling of charge carriers in MOS structures Au on p+-InAs with superthin (10-20 A) oxide film, the structures used in infrared photodetectors. In these structures the Schottky barrier provides near-surface inversion layer. The tunnel current-voltage (I-V) curves obtained at helium temperatures demonstrate the negative differential resistance region (NDR). We develop semiclassical two-band transfer matrix approach to the conversion tunneling analysis in a multilayer structure and calculate on its base the I-V curves dependence on the structure parameters. The NDR occurs to be caused by the motion of the remote quantum level in the inversion layer. The calculated I-V characteristics agree with the experimental ones quite well. The very existence of NDR and the shape of I-V curves depends strongly on the nature of localized electron states at the semiconductor interface. The characteristics of these electron states are used in the calculations as fitting parameters. Therefore, we suggest a new method for the interface states diagnosis. INTRODUCTION The superthin-oxide-layer MOS structures with the Schottky barrier based on InAs are of wide use in various electro-optical applications. These structures demonstrate quite interesting electrophysical properties, which seem to be caused by the Fermi level pinning at the surface of InAs near the conduction band edge. This pinning creates an n-type layer near the surface, the inversion layer for p-type InAs. As early as in [1] (and, later, in [2]) the region of negative differential resistance (NDR) had been found in the current-voltage (I-V) curve of such structures. This NDR behavior cannot be connected with the resonant tunneling in effective two-barrier structure [3], because the quantized electron level in the inversion layer occurs to lie higherthan the valence band top in the bulk. Neither competitive dependencies of the insulator and effective interband barriers on the applied voltage [2] nor thermostimulated tunneling via conduction band or phonon-assisted processes taking into consideration [4] occurred sufficient to pronounce this NDR. In this paper we suggest new physical mechanism (we called it virtual resonance) leading to NDR behaviour. To describe the effect quantitatively, we develop a semiclassical transfer matrix approach and find analytical expressions for the structure transmission coefficients. Making use of these coefficients, we calculate the I-V curves for the structure parameters of our experiment. The calculated curves agree quite well with the experimental ones. This new mechanism is highly sensitive to the localized electron states at the interface and may serve as a test for these states existence and nature. 443
Mat. Res. Soc. Symp. Proc. Vol. 448 01997 Materials Research Society
EXPERIMENT As substrates for the MOS structure fabrication we used p-InAs plates of crystallographic orientation and 1-5.101" cm- 3 dopant concentration. Three groups of samples
Data Loading...
