Nonlinear behavior of current‐dependent emission for diamond light‐emitting diodes

Abstract

Nonlinear emission characteristics of (111)‐oriented diamond p–i–n junction light‐emitting diodes (LEDs) were investigated. We measured the superlinear increase of excitonic emission and sublinear increase of deep‐level emission due to defects and/or impurity centers depending on injected current at room temperature (RT). These characteristics could not be explained by conventional carrier trapping and recombination processes at deep levels based on simple Shockley–Read–Hall statistics. We introduced three‐step processes of carrier trapping and recombination at charged deep levels via bound states, where the bound states are stable even at RT because of low dielectric constant in diamond. Rate equation analysis based on this concept simultaneously explained the superlinear increase of excitonic emission and sublinear increase of deep‐level emission for diamond LEDs.

Influence of substrate misorientation on the surface morphology of homoepitaxial diamond (111) films

“…Diamond semiconductors have been attracting much interest for application in high‐power devices and deep‐ultraviolet (DUV) light‐emitting diodes (LEDs) owing to their outstanding physical and electronic properties. For diamond‐based devices, homoepitaxial diamond (111) films have been garnering increasing interest because of the fabrication of high‐current‐density diodes , high‐voltage (10 kV) vacuum power switches , high‐efficiency DUV LEDs , and high‐biocompatible solution gate FET using un‐doped, boron‐doped, and/or phosphorus‐doped diamond (111) films grown by chemical vapor deposition (CVD). In addition, the nitrogen‐vacancy (NV) center in diamond has attracted significant interest owing to its excellent spin and optical characteristics for quantum devices .…”

4 A/cm², 7kV normally-off diamond-emitter vacuum switch

“…3, the band-edge electroluminescence due to free exciton recombination was observed. (invisible) [3,8,9] Thus, the quality of the i-layer was good enough for carriers to conduct in such a scale as 40 m, and then bipolar action should play an imporant role for the electron emission. However, when the surface was not hydrogen-terminated, electron emission was not obtained.…”

“…[2,3,7] Then we proposed that a diamond pin diode-type electron emitter (pin electron emitter) with an NEA surface was the most suitable one for ultra-high voltage vacuum switches, since conductivity modulation with high carrier density was expected during room temperature (RT) operation with the carriers overcoming the recombination at deep levels via high-density free exciton states as an unique property of diamond. [3,8,9] The electron emission from diamond pn or pin diodes with an NEA is based on a combination of (1) the NEA which keeps electron emission under a very low electric field, or low on voltage, during the on-state of the switch, (2) high electron injection operation of a pin diamond diode at RT with a hopping conduction in the p ++ -and/or n + -layer, [3,6,[8][9][10] and (3) good insulation of a vacuum. This paper presents our recent progress on the capability for high current operations of the vacuum switch to be close to the realization of ultra-high voltage vacuum switches.…”

Free exciton luminescence from a diamond p–i–n diode grown on a substrate produced by heteroepitaxy

“…According to their discussion, it is necessary to achieve enough low defect density, including both radiative and non‐radiative defects to realize the super‐linear increase in the band‐edge (free‐exciton) luminescence (Fig. ) .…”