Opto-electronic devices based on the negative differential resistance of GaAs/AlGaAs multiple quantum wells pin structure

Abstract

This thesis demonstrates novel optical logic operations with symmetric self electro-optic effect devices (S-SEEDs), and discusses the physics related to the optical logic operations and studies the feasibility of a novel optical information and processing system. Using an impulse photocurrent response function one can theoretically derive the minimum switching energy for various S-SEED structures. This approach provides a way to determine the optimum structure for the implementation of the devices such as a low drive-voltage, high operation power, device electrical parameters (resistance, inductance and capacitance) and simple device geometry. An impedance-matched asymmetric Fabry-Perot SEED with high power performance is investigated in terms of absorption saturation and ohmic heating problem. Although the operation power is one of the key parameters, the signal properties are degraded mainly by thermal and saturation effect. In order to lessen the problem, the most important condition was to reduce the drive-voltage. However, other parameters such as the signal difference, the contrast ratio, and the operation power have to be improved in terms of bit rate and noise characteristics for a practical switching scheme of various device structures. Utilizing multiple shallow quantum wells (MSQWs) instead of conventional MQWs structures improved the performance of the devices and exploited the fast sweep-out time and high absorption saturation power. A pin diode with stacked structure was constructed and the device showed optimized electric field swing and reduced driving voltage. This structure also showed a low switching energy and reduced thermal problem while maintaining signal properties, which were comparable with other conventional devices. An asymmetric Fabry-Perot (AFP) cavity was employed in the stacked pin-structure to obtain large contrast ratio comparable to that of the conventional pin-structure. A new device scheme without external bias voltage was d...