Resistive-Gate Aluminum Gallium Arsenide/gallium Arsenide Two-Dimensional Electron Gas Charge-Coupled Devices

Resistive-gate GaAs and AlGaAs/GaAs two-dimensional electron gas (2DEG) charge-couple devices (CCDs) for high speed analog signal processing and detector array readout applications are investigated. Numerical analysis on a capacitive-gate structure is performed to investigate gap-related potential trough problems encountered in capacitive-gate structure GaAs CCDs. Numerical modelling of carrier transport in a resistive -gate structure is also performed to investigate the speed performance of resistive-gate structure GaAs CCDs, demonstrating an interesting physical phenomenon of inhibited charge packet broadening induced by transferred-electron effects. Results of both analyses show promise of high-performance (high charge transfer efficiency and high speed) GaAs CCDs by the use of a resistive-gate structure. Characteristics of electron-beam evaporated Cr -SiO cermet films for resistive-gate CCDs are studied. Characteristics of a cermet/GaAs Schottky diode are measured and compared with those of Al/GaAs and Cr/GaAs Schottky diodes. The e-beam evaporated Cr-SiO cermet film exhibits excellent Schottky diode characteristics on GaAs, showing promise for use as a resistive layer in high-performance resistive -gate GaAs and related heterostructure CCDs. Resistive-gate two-dimensional electron gas (2DEG) CCDs with a four-phase clocking scheme are fabricated on uniform-doped and planar-doped AlGaAs/GaAs heterostructures. At room temperature, the uniform-doped and planar-doped AlGaAs/GaAs 2DEG CCDs exhibit a charge transfer efficiency (CTE) of 0.9990 from 13 MHz to 1 GHz (test station limit) and a CTE of 0.9997 from 13 kHz to 1 GHz, respectively. Extension of the low frequency operation limit of the planar-doped structure is achieved by a reduction of gate leakage current. A resistive-gate two-dimensional electron gas CCD with a two-phase clocking scheme is also fabricated and exhibits a CTE of 0.9993 at 26 MHz clock frequency. Gate leakage current of a planar-doped AlGaAs/GaAs heterostructure is investigated to predict the low frequency operation limit of this device at low temperature. Numerical analysis shows good agreement with experimental data, revealing that the gate leakage of this structure is dominated by thermionic field emission. A novel structure is suggested. According to the modelling, this structure has reduced gate leakage current by more than 6 orders of magnitude at room temperature and more than 9 orders of magnitude at lower temperatures compared with that of a planar-doped structure, suggesting possible ultra-low dark current operation of 2DEG CCDs fabricated on this structure. GaAs and related heterostructure charge-coupled devices for detector array readout multiplexer applications are described. Device design considerations for various types of advanced III-V infrared detector arrays are presented. Design examples of CCD readouts for linear and two-dimensional detector arrays with different methods and signal coupling schemes are presented.