Cooling Power Density of SiGe/Si Superlattice Micro Refrigerators

2003 ◽  
Vol 793 ◽  
Author(s):  
Gehong Zeng ◽  
Xiaofeng Fan ◽  
Chris LaBounty ◽  
Edward Croke ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Thin Film ◽  
Power Density ◽  
Heat Load ◽  
Room Temperature ◽  
Thermionic Emission ◽  
Cooling Power ◽  
Device Performance ◽  
Hot Carriers ◽  
Superlattice Structures ◽  
Load Conditions

ABSTRACTExperiments were carried out to determine the cooling power density of SiGe/Si superlattice microcoolers by integrating thin film metal resistor heaters on the cooling surface. By evaluating the maximum cooling of the device under different heat load conditions, the cooling power density was directly measured. Both micro thermocouple probes and the resistance of thin film heaters were used to get an accurate measurement of temperature on top of the device. Superlattice structures were used to enhance the device performance by reducing the thermal conductivity, and by providing selective emission of hot carriers through thermionic emission. Various device sizes were characterized. The maximum cooling and the cooling power density had different dependences on the micro refrigerator size. Net cooling over 4.1 K below ambient and cooling power density of 598 W/cm2 for 40 × 40 μm2 devices were measured at room temperature.

High Cooling Power Density of SiGe/Si Superlattice Microcoolers

2001 ◽  
Vol 691 ◽  
Author(s):  
Gehong Zeng ◽  
Xiaofeng Fan ◽  
Chris LaBounty ◽  
John E. Bowers ◽  
Edward Croke ◽  
...  
Keyword(s):  
Thin Film ◽  
Power Density ◽  
Room Temperature ◽  
Density Measurement ◽  
Thermionic Emission ◽  
Cooling Power ◽  
Thin Film Resistors ◽  
Fabrication And Characterization ◽  
Superlattice Structures

ABSTRACTFabrication and characterization of SiGe/Si superlattice microcoolers integrated with thin film resistors are described. Superlattice structures were used to enhance the device performance by reducing the thermal conductivity, and by providing selective emission of hot carriers through thermionic emission. Thin film metal resistors were integrated on top of the cooler devices and they were used as heat load for cooling power density measurement. Various device sizes were characterized. Net cooling over 4.1 K and a cooling power density of 598 W/cm2 for 40 × 40 μm2 devices were measured at room temperature.

P-type SiGe/Si Superlattice Cooler

2000 ◽  
Vol 626 ◽  
Author(s):  
Xiaofeng Fan ◽  
Gehong Zeng ◽  
Edward Croke ◽  
Gerry Robinson ◽  
Chris LaBounty ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermionic Emission ◽  
Single Element ◽  
Device Performance ◽  
Hot Carriers ◽  
Strained Si ◽  
Fabrication And Characterization ◽  
Superlattice Structures ◽  
P Type

ABSTRACTThe fabrication and characterization of single element p-type SiGe/Si superlattice coolers are described. Superlattice structures were used to enhance the device performance by reducing the thermal conductivity between the hot and the cold junctions, and by providing selective emission of hot carriers through thermionic emission. The structure of the samples consisted of a 3 μm thick symmetrically strained Si0.7Ge0.3/Si superlattice grown on a buffer layer designed so that the in-plane lattice constant is approximately that of relaxed Si0.9Ge0.1. Cooling up to 2.7 K at 25 °C and 7.2 K at 150 °C were measured. These p-type coolers can be combined with n-type devices that were demonstrated in our previous work. This is similar to conventional multi element thermoelectric devices, and it will enable us to achieve large cooling capacities with relatively small currents.

Characterization of Thin-film Thermoelectric Micro-modules using Transient Harman ZT Measurement and Near-IR Thermoreflectance

2007 ◽  
Vol 1044 ◽  
Author(s):  
Rajeev Singh ◽  
James Christofferson ◽  
Zhixi Bian ◽  
Joachim Nurnus ◽  
Axel Schubert ◽  
...  
Keyword(s):  
Thin Film ◽  
Heat Load ◽  
Figure Of Merit ◽  
Near Infrared ◽  
Device Performance ◽  
Metal Contacts ◽  
Thermoelectric Figure ◽  
Near Ir ◽  
Harman Technique

AbstractWe characterize several thin film thermoelectric micro-modules composed of 20 µm-thick elements and designed for cooling applications to identify factors that may limit device performance. Thermoelectric figure-of-merit measurements using the transient Harman technique are compared with maximum cooling data under no heat load. Correlation between the two measurements depending on the location of the parasitic joule heating in the module is analyzed. Near-infrared thermoreflectance is used to examine temperature non-uniformity in the module. The temperature distribution on the metal contacts due to the Peltier and Joule effects is obtained non-destructively through the silicon substrate of an active module.

Correlations Between YBa2Cu3O7-δ Thin Film Materials Properties and RF Device Performance

1997 ◽  
Vol 474 ◽  
Author(s):  
T. S. Kaplan ◽  
M. T. Salazar ◽  
Q. Huang ◽  
A. Barfknecht ◽  
Z. Lu
Keyword(s):  
Thin Film ◽  
Room Temperature ◽  
Second Phase ◽  
Device Performance ◽  
Rocking Curve ◽  
Phase Density ◽  
Materials Properties ◽  
Microstrip Resonators ◽  
Rf Performance ◽  
Lower Resistivity

ABSTRACTBetter knowledge of the relationships between YBa2Cu307-δ (YBCO) materials properties and the RF performance of devices made from these materials should lead to improved device performance and yields. A variety of materials tests were performed on our production YBCO films which were patterned into standard microstrip resonators. The materials parameters were then compared with the unloaded Q of the resonators at 77 K. As expected, films with higher Q's tended to have higher Tc, higher Jc, greater film thickness, and better crystallinity. The last was based on narrower YBCO rocking curve peak, lower second phase density (judged by lower resistivity and greater θ-2θ (005) peak area), and a narrower θ-2θ (005) peak. The room temperature sheet resistance was found to be a useful predictor of microwave performance for films that are otherwise similar.

Experimental Investigation of Thin Film InGaAsP Coolers

2000 ◽  
Vol 626 ◽  
Author(s):  
Christopher J. LaBounty ◽  
Ali Shakouri ◽  
Gerry Robinson ◽  
Luis Esparza ◽  
Patrick Abraham ◽  
...  
Keyword(s):  
Thin Film ◽  
Three Dimensional ◽  
Optoelectronic Devices ◽  
Thermionic Emission ◽  
Optical Power ◽  
Peltier Effect ◽  
Material System ◽  
Monolithically Integrated ◽  
Cooling Behavior ◽  
Superlattice Structures

ABSTRACTMost optoelectronic devices for long haul optical communications are based on the InP/InGaAsP family of materials. Thin film coolers based on the same material system can be monolithically integrated with optoelectronic devices such as lasers, switches, and photodetectors to control precisely the device characteristics such as wavelength and optical power. Superlattice structures of InGaAs/InP and InGaAs/InGaAsP are used to optimize the thermionic emission resulting in a cooling behavior beyond what is possible with only the Peltier effect. A careful experimental study of these coolers is undertaken. Mesa sizes, superlattice thickness, and ambient temperature are all varied to determine their effect on cooling performance. A three-dimensional, self-consistent thermal-electric simulation and an effective one-dimensional model are used to understand the experimental observations and to predict what will occur for other untested parameters. The packaging of the coolers is also determined to have consequences in the overall device performance. Cooling on the order of 1 to 2.3 degrees over 1-micron thick barriers is reported.

Enhanced Cooling in Doped Semiconductors Due to Nonlinear Peltier Effect

2007 ◽  
Vol 1044 ◽  
Author(s):  
Mona Zebarjadi ◽  
Keivan Esfarjani ◽  
Ali Shakouri
Keyword(s):  
Applied Field ◽  
Room Temperature ◽  
Nonlinear Term ◽  
Peltier Effect ◽  
Cooling Power ◽  
Device Performance ◽  
Heat Current ◽  
Doped Semiconductors ◽  
The Third ◽  
Peltier Coefficient

AbstractThermoelectric coefficients become a function of the applied field and temperature gradient if the latter become large enough. So in analyzing device performance in this regime accurately, it is important to include the non-linear terms. Non-linearity is a consequence of electron heating. For low doping concentrations, nonlinearity can happen at low currents. We will show that at room temperature in InGaAs it starts at practical currents on the order of 105 A/cm2. At low temperatures the Peltier coefficient goes to zero. However, its nonlinear term does not change as much. Since the nonlinear heat current goes with the third power of current, there is a chance that in some cases it can overcome the joule heating. We will show that at T=77K the cooling power can be enhanced by a factor of seven compared to room temperature. Nonlinearity of the Seebeck coefficient becomes an important factor when high temperature gradients are applied on nanoscale samples, and can lead to enhanced power generation

Conservation of Lateral Momentum in Heterostructure Integrated Thermionic Coolers

2001 ◽  
Vol 691 ◽  
Author(s):  
Daryoosh Vashaee ◽  
Ali Shakouri
Keyword(s):  
Quantum Well ◽  
Power Factor ◽  
Bulk Material ◽  
Theoretical Calculations ◽  
Thermionic Emission ◽  
Hot Electrons ◽  
Cooling Power ◽  
Emission Process ◽  
Wide Range ◽  
Superlattice Structures

ABSTRACTThin film thermionic coolers use selective emission of hot electrons over a heterostructure barrier layer from emitter to collector resulting in evaporative cooling. In this paper a detailed theory of electron transport perpendicular to the multilayer superlattice structures is presented. Using Fermi-Dirac statistics, density-of-states for a finite quantum well and the quantum mechanical reflection coefficient, the currentvoltage characteristics and the cooling power density are calculated. The resulting equations are valid in a wide range of temperatures and electric fields. It is shown that conservation of lateral momentum plays an important role in the device characteristics. If the lateral momentum of the hot electrons is conserved in the thermionic emission process, only carriers with sufficiently large kinetic energy perpendicular to the barrier can pass over it and cool the emitter junction. However, if there is no conservation of lateral momentum, the number of electrons participating in thermionic emission will dramatically increase. The theoretical calculations are compared with the experimental dark current characteristics of quantum well infrared photodetectors and good agreement over a wide temperature range is obtained. Calculations for InGaAs/InGaAsP superlattice structures show that the effective thermoelectric power factor (electrical conductivity times the square of the effective Seebeck coefficient) can be improved comparing to that of bulk material. We will also discuss methods by which the conservation of lateral momentum in thermionic emission process can be altered such as by creating a controlled roughness at the interface of the superlattice barriers. The improvement in the effective power factor through thermionic emission can be combined with the other methods to reduce the phonon thermal conductivity in superlattices and thus obtain higher thermoelectric figure-of-merit ZT.

3D Electrothermal Simulation of Heterostructure Thin Film Micro-Coolers

2003 ◽  
Author(s):  
Yan Zhang ◽  
Daryoosh Vashaee ◽  
James Christofferson ◽  
Ali Shakouri ◽  
Gehong Zeng ◽  
...  
Keyword(s):  
Thin Film ◽  
Contact Resistance ◽  
Room Temperature ◽  
Cooling Power ◽  
Semiconductor Substrate ◽  
Promising Candidate ◽  
Key Factor ◽  
Electrothermal Simulation ◽  
Spot Cooling ◽  
Semiconductor Contact

A 3D electrothermal model is used to simulate and optimize Si/SiGe superlattice heterostructure micro-coolers. The model considers thermoelectric/thermionic cooling, heat conduction and Joule heating. It also includes non-ideal effects, such as contact resistance between metal and semiconductor, substrate/heatsink thermal resistance, the side contact resistance. The simulated results match very well with the experimental cooling curves for various device sizes ranging from 60×60μm2 up to 150×150μm2. It is found that the key factor limiting maximum cooling is metal semiconductor contact resistance. The maximum cooling could be doubled if we remove the metal-semiconductor contact resistance. The thin film Si/SiGe superlattice micro-coolers can provide cooling power density over 500 W/cm2 as compared with a few W/cm2 of bulk Bi2Te3 themoelectric coolers. This micro-cooler experimentally demonstrated a maximum cooling of 4.5°C at room temperature and 7°C of cooling at 100°C ambient temperature. It is a promising candidate for microprocessor spot cooling.

Studies on Water in the Hydration Chamber of a Modified Electron Microscope

1970 ◽  
Vol 28 ◽  
pp. 544-545
Author(s):  
R. C. Moretz ◽  
G. G. Hausner ◽  
D. F. Parsons
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Electron Microscope ◽  
Steady State ◽  
Room Temperature ◽  
Small Mass ◽  
Equilibrium Pressure ◽  
Biological Objects ◽  
Mechanical Pump ◽  
Differential Pumping

Use of the electron microscope to examine wet objects is possible due to the small mass thickness of the equilibrium pressure of water vapor at room temperature. Previous attempts to examine hydrated biological objects and water itself used a chamber consisting of two small apertures sealed by two thin films. Extensive work in our laboratory showed that such films have an 80% failure rate when wet. Using the principle of differential pumping of the microscope column, we can use open apertures in place of thin film windows.Fig. 1 shows the modified Siemens la specimen chamber with the connections to the water supply and the auxiliary pumping station. A mechanical pump is connected to the vapor supply via a 100μ aperture to maintain steady-state conditions.

Sign in / Sign up

Export Citation Format

Share Document