We investigated the current-voltage characteristics of the double barrier, resonant tunneling structure, using a self-consistent method. We note the significance of the effects of band bending and buildup of space charge in the quantum well. For the peak current, our calculated results agree with the measured results very well. However, the measured valley current is much greater than the calculated values.

We study the electronic properties of submicron vertical resonant tunneling structures containing several self-assembled InAs quantum dots (SADs) surrounded by four gate electrodes. The four gates are designed not only to squeeze the conductive channel containing a few SADs but also to differently modulate the electrochemical potential of each SAD. We measure the stability diagram and distinguish the features of lateral interdot coupling, such as the type of coupling (quantum mechanical or capacitive), the number of coupled dots, and the relative coupled dot position. This technique will be useful in characterizing the electronic properties of coupled SAD systems.

The Schottky diode characteristics of WSix contacts on n-type GaAs have been investigated and correlated to the film stress in WSix and crystallographic properties of the film. Experimental results show that (1) the high-temperature stability of WSix/GaAs Schottky diode characteristics depends significantly on Si content; (2) WSix/GaAs contacts exhibit very high-temperature-stable Schottky diode characteristics at Si content around 0.60, and at this Si content no metallurgical interactions between WSix and GaAs are observed by 2-MeV 4He+ Rutherford backscattering (RBS) measurements; (3) the optimum Si content for Schottky diode characteristics coincides with that for stress minimum in WSix; (4) the Schottky diode characteristics are not affected by whether WSix is crystallized or not, and a common feature of the regions where the Schottky diode characteristics are very high-temperature stable is that each consists of single-phase (W5Si3 secondary solid solution or amorphous).

The electrical and optical measurements of low-frequency characteristics for the GaAs MESFET structures with long gate width were found to be an effective tool for the studies of interface states between insulating films and GaAs. The surface leakage current through the interface layer plays an important role in the frequency dependence of the transconductance and the gate admittance. An equivalent circuit which quantitatively explains the experimental results is proposed. Using the MESFET structure overcoated with insulating films (SiO2, Si3N4, and AlN), electrical and optical properties of the interface between these insulating films and GaAs were studied and it was found that these films have characteristic activation energies of 0.62, 0.44, and 0.27 eV, respectively.

Influence of transition metal impurities on oxygen precipitation in Czochralskigrown silicon