Integrated on-chip gallium arsenide schottky diode and antenna for application in proximity communication system

Abstract

The objective of this research is to investigate the possibility of direct integration between III–V based materials of Schottky diode and planar antenna without any insertion of the matching circuit by applying direct connection through Coplanar Waveguide (CPW) structure. Gallium Arsenide (GaAs) and integrated onchip Schottky diode and antenna are considered as the promising material and device structure, to achieve such purposes. This kind of device structure should be able to function as wireless power supply as well as power detector. To achieve this objective, several basic components were studied. Firstly, the design, fabrication and characterization of individual Schottky diode and planar antenna were conducted in order to understand both Direct Current (DC) and Radio Frequency (RF) characteristics. RF signals were well detected and rectified by the fabricated Schottky diodes with the cut-off frequency of up to several tens GHz, and a stable DC output voltage was generated. The RF characteristics of planar dipole and meander antenna as a function of antenna dimension were investigated. Good return loss was obtained at the resonant frequency of the antenna. From the direct injection experiment, the conversion efficiency up to 80 % of 1 GHz signal to the diode was achieved. Then, the integrated device was evaluated by transmitting RF signal from a different planar antenna and also using a horn antenna placed at a certain distance. The irradiated signal was successfully received by the planar antenna and rectified by the integrated diode. The rectification achieved was due to enough power received by the antenna to turn on the diode (Schottky barrier height = 0.381 eV- Cr/Au metallization, turn on voltage = 0.8 V). The output voltage of several volts (V) was generated at the load which was connected in parallel to the diode. A maximum output voltage of around 0.6 V and 130 mV were generated at the load resistance for frequency of 2 GHz and 7 GHz, respectively. A closed-form equation for the conversion efficiency of the Schottky diode has been derived to analyse the diode for the high frequency rectenna. The measured results were in good agreement with calculated results with small discrepancy between them due to resistance blow up effect, effect of non-linear junction capacitance, effect of the finite forward voltage drop and the breakdown voltage of the diode. From these presented results, the proposed on-chip AlGaAs/GaAs HEMT Schottky diode and antenna seems to be a promising candidate to be used for application in proximity communication system as a wireless low power source as well as a highly sensitive RF detector device.