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Smith, Trevor

Publications and source records attributed to Smith, Trevor.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Analysis of the dependence of critical electric field on semiconductor bandgap

Abstract Understanding of semiconductor breakdown under high electric fields is an important aspect of materials’ properties, particularly for the design of power devices. For decades, a power-law has been used to describe the dependence of material-specific critical electrical field ( $${\mathcal{E}}_{\text{crit}}$$ E crit ) at which the material breaks down and bandgap ( E g ) . The relationship is often used to gauge tradeoffs of emerging materials whose properties haven’t yet been determined. Unfortunately, the reported dependencies of $${\mathcal{E}}_{\text{crit}}$$ E crit on E g cover a surprisingly wide range in the literature. Moreover, $${\mathcal{E}}_{\text{crit}}$$ E crit is a function of material doping. Further, discrepancies arise in $${\mathcal{E}}_{\text{crit}}$$ E crit values owing to differences between punch-through and non-punch-through device structures. We report a new normalization procedure that enables comparison of critical electric field values across materials, doping, and different device types. An extensive examination of numerous references reveals that the dependence $${\mathcal{E}}_{\text{crit}}$$ E crit ∝ E g 1.83 best fits the most reliable and newest data for both direct and indirect semiconductors. Graphical abstract

36 MATERIALS SCIENCE↗
DOE OSTI2022

Identification of the defect dominating high temperature reverse leakage current in vertical GaN power diodes through deep level transient spectroscopy

Deep level defects in wide bandgap semiconductors, whose response times are in the range of power converter switching times, can have a significant effect on converter efficiency. We use Deep Level Transient Spectroscopy (DLTS) to evaluate such defect levels in the n- drift layer of vertical GaN (v-GaN) power diodes with VBD ~ 1500 V. DLTS reveals three energy levels that are at ~0.6 eV (highest density), ~0.27 eV (lowest density) and ~ 45 meV (a dopant level) from the conduction band. Dopant extraction from Capacitance-Voltage measurement test (C-V) at multiple temperatures enables trap density evaluation, and the ~0.6 eV trap has a density of 1.2 × 10 15 cm -3 . Here, the 0.6 eV energy level and its density are similar to a defect that is known to cause current collapse in GaN based surface conducting devices (like HEMTs). Analysis of reverse bias currents over temperature in the v-GaN diodes indicates a predominant role of the same defect in determining reverse leakage current at high temperatures, reducing switching efficiency.

42 ENGINEERING↗