Heterostructure-integrated thermionic cooling of optoelectronic devices

Active refrigeration of optoelectronic components through the use of heterostructure integrated thermionic emission cooling is proposed and investigated. Enhanced cooling power compared to the thermoelectric effect of the bulk material is achieved through thermionic emission of hot electrons over a heterostructure barrier layer. These heterostructures can be monolithically integrated with other devices made from similar materials. The advantages of this type of integrated cooling as well as heterogeneous integration are discussed. From careful theoretical analysis, practical design guidelines are developed and applied to several thermionic cooler structures. Cooling performance is investigated for various device parameters and operating conditions. Several important non-ideal effects are identified such as contact resistance, heat generation and conduction in the wire bonds, and the finite thermal resistance of the substrate. These non-ideal effects are studied both experimentally and analytically, and the limitations induced on performance are considered. Full three-dimensional self-consistent thermal/electrical simulations are used to optimize the non-ideal effects. Several optoelectronic devices have been integrated with these coolers, and the results are presented. Thermionic emission cooling in heterostructures is shown to provide cooling of several degrees Celsius and cooling power densities of several 100's W/cm2. These micro-refrigerators can provide control over device characteristics such as output power, wavelength, and maximum operating temperature.