High RF-to-DC conversion efficiency of up to 50% was obtained with series connection between the diode and the load [15].In this paper, we report the RF-to-DC characteristics of a Schottky diode where the diode and load are connected in parallel under direct injection of the RF signal. The rectifying characteristics of the Schottky diode where the signal is irradiated from different transmitting dipole antennas to the integrated dipole antenna are also reported. This experiment was conducted in order to understand the performance of the integrated devices for real practical applications. The results show the potential breakthrough for direct on-chip integration towards realization of low power rectenna devices for their advanced heterogeneous integration on a Si platform.2.
?Fabrication of the Integrated DeviceAn n-AlGaAs/GaAs HEMT structure has been chosen as a substrate. This structure is capable of providing higher electron mobility due to its two-dimensional electron gas (2DEG) layer defined at the interface of the n-doped AlGaAs layer and undoped GaAs layer. Therefore, the n-AlGaAs/GaAs HEMT structure is promising for the fabrication of high-speed and high-frequency devices. Co-integration of various kinds of functional devices including rectenna devices on the same core material structure is more practical in terms of fabrication processes and cost. Thus, the development of rectenna devices based on such a structure has been considered in this study.In this work, we fabricated the CPW and dipole antenna structure on the semi-insulated (SI) GaAs layer, and not directly on the n-type HEMT structure, as shown in Figure 1a.
The HEMT structures was etched to the SI layer during the process of mesa formation by using a mixture of sulphuric acid, H2SO4, hydrogen peroxide (H2O2) and deionized (DI) water at Drug_discovery 25 ��C for 18 s. Formation of CPW and the dipole antenna on a SI layer seems to reduce the RF losses as the signal is travelling through the CPW. The details of the materials and the fabrication processes have been described in [10,15,31]. Figure 1b shows the top-view photo of the rectenna device. Table 1 summarizes the device dimensions and the operating frequencies. The CPW structure was designed so that it produces the characteristic impedance, Z0, of 50 ��. This CPW structure also permits direct injection of the RF signal through a Cascade GSG Infinity-150 microprober.Figure 1.(a) Schematic and (b) top view photo of the rectenna device.Table 1.Device dimensions and operating frequencies of the Schottky diode and antenna.3.?Result and Discussion3.1.