This paper presents a review of models of the current transport in different kind of heterojunctions (HJs) and their characteristics. In order to effectively deduce the dominant electron transport for the HJs based on ZnO or Zn1−xMgxO layers grown on Si substrate by MBE a comparison is performed – which type of the HJ exhibits better electrical properties. The current–voltage characteristics for the studied HJs were measured within 280–300 K. The transport properties of the HJs are explained in terms of Anderson model with reference to aforementioned current transport models. It is found, that the mechanisms of current transport for all of the studied HJs are similar. At a low forward voltage bias the tunneling current dominates while at medium voltage bias (0.5–1 V) multitunneling capture-emission prevails with the electron trap located at 0.1–0.25 eV below the bottom of a ZnO (Zn1−xMgxO) conduction band. Beyond this voltage bias space charge limited current governs the current transport.
A survey of breeding birds was carried out during the summer 1997-98 in several localities of the northern Danco Coast, Antarctic Peninsula. A total of 10 species were recorded: Pygoscelis antarctica (3234 pairs), P. papua (1888), Macronectes giganteus (76), Daption capense (61), Oceanites oceanicus (104), Phalacrocorax bransfieldensis (92), Ononis alba (15), Catharacta maccormicki (168), Lams dominicanus (583) and Sterna vittata (160 pairs).
This electronic paper presents an innovative technology for efficient use of the radio spectrum. This new frequency reconfigurable rotatable antenna is intended for wireless applications such as WLAN, WiMAX and Bluetooth mobile applications. The working principle of this proposed work is to print square patches mounted on the same circular dielectric substrate feed by a proximity coupling to eliminate the noise signal transmission and problems related to interference. The three positions correspond to an operating frequency controlled by a bipolar step-by-step engine. An optimization of the structure using the FEM finite element method as well as a comparison with other structures recently realized are detailed in this paper. The final numerical simulation results are: WLAN 4.95-5.53 GHz (BW = 11%) Gain = 6.06 dBi, WiMAX 3.35-3.75 GHz (BW = 11.2%) Gain = 7.48 dBi and Bluetooth 2.3-2.51 GHz (BW = 8.7%) Gain = 17.78 dBi.