A new room temperature wet chemical digital etching technique for GaAs is presented which uses hydrogen peroxide and an acid in a two‐step etching process to remove GaAs in approximately 15 Å increments. In the first step, GaAs is oxidized by 30% hydrogen peroxide to form an oxide layer that is diffusion limited to a thickness of 14 to 17 Å for time periods from 15 to 120 s. The second step removes this oxide layer with an acid that does not attack unoxidized GaAs. These steps are repeated in succession until the desired etch depth is obtained. Experimental results are presented for this digital etching technique demonstrating the etch rate and process invariability with respect to hydrogen peroxide and acid exposure times.

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The direct band energy (Eg) and donor–acceptor (D,A) transition energies are mapped as a function of temperature for Be-doped GaAsSb lattice matched to InP. Photoluminescence (PL) measurements over the temperature range 2 K≤T≤300 K yield two emission peaks, one of lower intensity and one of higher intensity. The lower intensity peak is believed to be Be related, while the higher intensity peak is from residual impurities. The emission energies of both PL peaks increase linearly with respect to the logarithm of excitation intensity, indicating the peaks are (D,A) transitions. Measurement of Eg was achieved using optical absorption spectroscopy over the range 14 K≤T≤300 K. A least squares fit of the absorption data using the Varshni equation produces a closed form expression for Eg(T) with coefficients α=13.5×10−4 eV/K, and β=135 K.

MOCVD and MBE grown GaN were implanted with Ar, Mg, Si, Be, C, and O, and annealed in a conventional oven under flowing NH3 or N2 gas. Absorption measurements confirmed that implantation damage was annealed out after 90 minutes at a temperature of 1000 °C. Surface damage caused by NH3 annealing was evident in absorption and photoluminescence measurements for annealing temperatures of over 1000 °C. Although most of the implants showed no unique luminescence peaks, systematic changes in the relative intensities of the exciton, donor-acceptor pair, and yellow peaks were noted. The Mg implanted samples showed evidence of the acceptor bound exciton line at 3.44 eV, and a unique peak at 3.3 eV possibly due to a Mg free-to-bound transition.

Ferroelectric (FE) Barium Strontium Titanate (Ba (1-x) Sr x TiO 3 , BST) thin film varactor technology is applied to the antenna miniaturization and reconfiguration successfully. CPW square-ring slot antenna is used as a design example, and antennas with and without integrated BST varactors were fabricated and characterized. Including the total ground, the size of miniaturized antenna is 0.12λ 0 ×0.12λ 0 which is reduced by 31% compared with antenna without the BST varactors. Moreover, the frequency of the miniaturized antenna with the BST varactors is reconfigurable from 5.8GHz to 6.1GHz with a low DC biasing voltage of 3V. Both E-plane and H-plane patterns were measured for the antennas. Fabrication details and measurement setup are also presented.Index Terms -Ferroelectric, thin film, antenna miniaturization, reconfigurable antenna, coplanar waveguide (CPW), ring slot antenna, varactor loading, high permittivity material.