AlGaN/6H-SiC heterojunction bipolar transistors (HBTs) were fabricated, and the device performance as well as the
electrical properties of the n-AlGaN/p-SiC heterojunction were studied by temperature dependent current-voltage
characterization. Current gain β=I<sub>C</sub>/I<sub>B</sub> calculated from <i>I-V</i> characteristics varied from sample to sample in the range of
75-100. A barrier height of 1.1 eV is derived from the Arrhenius plot and its origin is discussed.
The conduction band offset of n-ZnO/n-6H-SiC heterostructures prepared by rf-sputtered ZnO on commercial n-type
6H-SiC substrates has been measured. Temperature dependent current-voltage characteristics, photocapacitance, and
deep level transient spectroscopy measurements led to conduction band offsets of 1.25 eV, 1.1 eV, and 1.22 eV,
Lead zirconate titanate PbZr<sub>52</sub>Ti<sub>48</sub>O<sub>3</sub> (PZT) layers were deposited on ZnO layers by rf-sputtering at varying substrate temperatures. The effect of annealing on PZT crystal properties has been studied by X-ray diffraction and atomic force
microscopy. It is shown that the annealing in oxygen ambient has significant effect on the quality of the deposited PZT
layers. The optimum growth temperature has been found to be 650 C.
Electrical properties of n-ZnO/n-GaN isotype heterostructures prepared by rf-sputtering of ZnO films on GaN layers
which in turn grown by metal-organic vapour phase epitaxy are discussed. Current-voltage <i>(I-V)</i> characteristics of the n-
ZnO/n-GaN diodes exhibited highly rectifying characteristics with forward and reverse currents being ~1.43x10<sup>-2</sup> A/cm<sup>2</sup>
and ~2.4x10<sup>-4</sup> A/cm<sup>2</sup>, respectively, at ±5 V. From the Arrhenius plot built representing the temperature dependent
current-voltage characteristics (<i>I-V-T</i>) an activation energy 0.125 eV was derived for the reverse bias leakage current
path, and 0.62 eV for the band offset from forward bias measurements. From electron-beam induced current
measurements and depending on excitation conditions the minority carrier diffusion length in ZnO was estimated in the
range 0.125-0.175 &mgr;m. The temperature dependent EBIC measurements yielded an activation energy of 0.462 ± 0.073
Ferroelectric field effect transistors (FFETs) with hysteretic I-V characteristics were attained with 25 nm thick Pb(Zr<sub>0.52</sub>Ti<sub>0.48</sub>)O<sub>3</sub> (PZT)/Si<sub>3</sub>N<sub>4</sub> gated AlGaN/GaN heterostructure. The PZT films used in the gate of the device was deposited by magnetron rf-sputtering at the substrate temperature of 700 <sup>o</sup>C. Increasing the PZT deposition temperature from that in previous device structures from 600 <sup>o</sup>C to 700 <sup>o</sup>C we obtained much improved device performance in terms of the IV characteristics inclusive of hysteretic behavior. The pinch-off voltage was about 7 V in FFET device compared to 6 V in a the control (conventional) AlGaN/GaN device. Counterclockwise hysteresis appeared in the transfer characteristic curve of a FFET with a maximal drain current shift of about 10 mA at the gate-to-source voltage of -6 V.