Current-induced electrical efficiency degradation (EED) is identified as a strong power conversion efficiencylimiting factor for vertical blue InGaN-on-SiC light-emitting diodes (LEDs). It is found that EED is caused by an increase in series resistance that follows current crowding. EED starts at the moderate-current domain (≥ 10 −3 A) and limits the power conversion efficiency at the level of ≤75% in the high-current domain (>1.0 A). By decreasing current spreading length, EED also causes the optical efficiency to degrade and stands for an important aspect of the vertical LED's performance.

The authors show that the performance of red vertical AlGaInP/GaAs light-emitting diodes is compromised by the current crowding (CC) effect in the moderate-current (space charge region dominates in the device performance) and high-current (series resistance dominates in the equivalent circuit of a device) domains. Depending on the contact pattern, a remarkable part of the performance degradation comes as a result of the electrical power lost on the series resistance ( 17%). CC affects the ideality factor and causes the current spreading length to decrease from 425 m at low currents to 75 m at a current of 250 mA.

We propose and demonstrate a coding-decoding procedure as an important step to realize one more Si-based photonic device. Low-fluence (<1014 e/cm2) high-energy (1 MeV) electron irradiation of a bulk Si matrix is used to code an information by forming local regions with lower free carrier lifetime that are hidden under the surface and invisible to the eye. Short-wavelength (<1 μm) free carrier generation stands for multiple, remote, and nondestructive decoding process, which makes it easy to dynamically (ms range) visualize a code by capturing two-dimensional pattern of thermal emission in the longer-wavelength (3–12 μm) band (light down conversion).