Experimental procedure

All GaAsN films were grown by CBE on high conductive n – or p-type GaAs 2° off toward [010] substrate using Triethyl gallium ((C2H5)3Ga, TEGa), Trisdimethylaminoarsenic ([(CH3)2N]3As, TDMAAs), and Monomethylhydrazine (CH3N2H3, MMHy) as Ga, As, and N sources, respectively. The flow rates TEGa = 0.1 sccm and TDMAAs = 1.0 sccm were considered as conventional values. The growth temperatures of 420 °C and 460 °C were used for p-type and n-type GaAsN, respectively. Concerning the doping, p-type GaAsN films are unintentionally doped. The n-type alloys were obtained using a silane (SiH4) source or by growing the films under lower MMHy and high growth temperature.

Three different device structures are used in this study: (i) n- and p-type GaAsN schottky contacts, (ii) n+-GaAs/p-GaAsN/p-GaAs, and (iii) n-GaAsN/p+-GaAs hetro-junctions. The N concentration in all GaAsN layers was evaluated using XRD method. Aluminum (Al) dots with a diameter of 0.5/1 mm were evaporated under vacuum on the surface of each sample. Alloys of Au-Ge (88:12 %) and Au-Zn (95:05 %) were deposited at the bottom of n-type and p-type GaAs substrates for each device, respectively. Some samples were treated by post­thermal annealing under N2 liquid gas and using GaAs cap layers to avoid As evaporation from the surface. The temperature and the time of annealing will be announced depending on the purpose of making annealing. The background doping and the doping profile in the extended depletion region under reverse bias condition were evaluated using the capacitance-voltage (C-V) method. The leakage current in all used samples ranged from 0.3
nA to 10 ^иА for a maximum reverse bias voltage of -4 V. A digital DLTS system Bio-Rad DL8000 was used for DLTS and C-V measurements. The activation energy Et and the capture cross section <jn, p were determined from the slope and the intercept values of the Arrhenius plot, respectively.

Updated: August 21, 2015 — 12:03 pm