Research Of One Bifacial Gaas Photoconductive Semiconductor Switch With Low Contact Resistivity

Photoconductive semiconductor switches (PCSS) is a kind of semiconductor material switch controlled by light (Optically Controlled Photoconductive semiconductor switch). The photoconductive switches is a kind of photoelectric conversion device which can generate electrical pulses using the change of the PCSS semiconductor material’s conductivity when given a laser excitation. PCSS has the advantages of high power density (MW magnitude), fast response (ps magnitude), low trigger jitter (ps magnitude), anti-electromagnetic interference ability (good optical isolation), small size and is easy to integrate. It has been widely used in high current ignition devices, denial weapons and high-power microwave systems, precision time synchronization, THz technology, transient testing, impulse radar field, electromagnetic interference and attack systems.Researchers are studying the materials for different purposes photoconductive switches tirelessly since the birth of PCSS, the experiments and research for materials has never been stopped. The first generation of semiconductor material Si, the second-generation semiconductor material GaAs and the third generation of semiconductor material of SiC have been widely applied in the photoconductive switches.GaAs has a much higher electron mobility than Si and SiC which is up to 8500 cm2/V·s at room temperature. It also has a carrier lifetime between a few tenths ns to a few ns. The experimental data indicate that GaAs photoconductive switch has a higher voltage conversion efficiency with the light excitation of average wavelength.The core of the PCSS is the ohmic contact formed by heavily doped semiconductor active region and the layer electrode metal formed with the alloying process. The magnitude of the contact resistance of the electrode directly determines the performance of the photoconductive switch, thus accurate measurement of PCSS ohmic contact parameters is the prerequisite of the PCSS studies.The properties of the ohmic contact can be embodied by the IV curve and the contact resistivity measurements, also it can be represented by scanning its morphology characterization with microscope. In order to obtain good performance of a device, we must reduce the contact resistivity of the device as much as possible, so we can reduce the contact and increase the voltage reducing of the working portion of the device.The research of this paper is mainly focused on the manufacture craft of GaAs photoconductive switches and the performance analysis of ohmic contacts.This paper described the study meaning, structure and application of the photoconductive switches, and beside that the principle of the PCSS and ohmic contact were introduced. After that the substrate material of the photoconductive switch, the electrode metal systems and the structure of the photoconductive switch had been determined with the contrasts to meet the project’s requirements. Then the measurements method of common ohmic contact resistivity and the production process of photoconductive switches were introduced. Next the contact resistance of the sample was measured using circle dot transmission line measurement; the Ⅳ characteristics of ohmic contact was measured with the semiconductor electrical characteristics tester; and the morphology of metal electrode was scanned by AFM atomic scanning microscope. Finally, the research work of this paper is summarized and discussed.