TemperatureDependent Tranient Capacitance in …依赖于温度的瞬态电容….pptVIP

Temperature-Dependent Transient Capacitance in InGaAs/InP-based Diodes Kiril Simov and Tim Gfroerer Davidson College Mark Wanlass NREL Supported by the American Chemical Society – Petroleum Research Fund Motivation: Thermophotovoltaics Experimental Setup P-N Junction Depletion Layer with Bias Typical Capture Data –Dependence on Pulse Length Capture Analysis Number of Traps Typical Escape data – Dependence on Temperature Escape Analysis Conclusions A deep level has been detected The effective trap cross-section is ~10-20 cm2 The trap concentration is ~ 1016 cm-3 The depth of the level is ~ 0.30 eV Our results are consistent with sub-bandgap PL from similar structures. Web links: This talk: /faculty/thg/talks-posters/MAR-04.ppt PL poster: /faculty/thg/talks-posters/SESAPS-03.ppt Device Structure * * Photovoltaic Cell Heat Source Blackbody Radiator Thermal Radiation Blackbody Radiation Computer with LabVIEW Temp Controller Pulse Generator Cryostat with sample Digital Scope(Tektronix) (1) (2) (3) (4) (5) Oxford 77K Agilent Capacitance meter (Boonton) Depletion Layer With Bias Depletion Layer - - - + + + P N + + + + + + + + + + + + + + + + + + + + + + + + - - - - - Holes: s = 2.5 x 10-20 cm2 Electrons: s = 7.5 x 10-21 cm2 Capture cross-section ~ 7 x 1015 cm-3 D ~ trap depth p+ layer n layer junction THIS IS THE MOST IMPORTANT SLIDE!!! The concept behind applying a bias pulse is that it expands the depletion layer, which changes the capacitance of the device. This gives the mobile charge carriers a chance to move to a new region of the diode. Once they get to this new region, there is the possibility that they will be trapped. By measuring the time it takes for the capacitance to change, we study how charges move into and out of traps, and the capture cross section and the depth of the traps can be determined. As the negative side is loosely populated, the depletion layer extends more into the negative side, once again as indicated in the drawing. The p sid