Sergei Shapoval

Effect of nonuniform current injection on electroluminescence spectra of InGaN-GaN blue-green light-emitting diode

Blue-green InGaN/GaN light-emitting diodes (LEDs) with spatially nonuniform current injection were fabricated and tested. Broad electroluminescence (EL) spectra with equal peak intensities of blue and green emission lines and shallow trough between them were observed at elevated injected current. These features of EL-spectrum are believed to be caused by the mesh-like patterning of the electrode as it creates spatially nonuniform electric potential which provides spatial modulation of the injected current along the QW-planes. The latter results not only in spatial nonuniformity of intensity of generated light along the QW-planes but due to screening of polarization field in the QWs causes also position-dependent blue shift of EL. The observed phenomenon can be used to control the EL spectra of dual-wavelength LEDs by the patterned electrodes.

Impact of mesh-like top p-electrode on output performance of light-emitting diode: Numerical study

Numerical model and procedure for the light-emitting diode (LED) with realistic mesh strips having square cross-section are developed and used for simulation of electrical and output optical characteristics at different dimensions of the mesh and bias voltages. Performances simulated for realistic square cross-section strips and analytical model based on the finite-radius wire approximation were compared. Comparison demonstrates the advantages of realistic model, in particular, for extraction of the mesh-like electrode parameters resulting in maximum optical output.

Numerical analysis of planar light-emitting diode with designed p-electrode

Light-emitting diode (LED) with designed metal electrode to the top p-semiconductor layer is studied. Original numerical model and procedure are developed for the LED with nonuniform distributions of electrical and optical characteristics caused by the mesh-like configuration of the top electrode. The proposed approach can be used to optimize the LED ouput optical performance by proper choice of the geometrical parameters of the meshed electrode.

Modeling of light-emitting diode with nonuniform current injection

Light-emitting diode (LED) with nonuniform current injection caused by the mesh-like design of top metal electrode is studied numerically. Three-dimensional Laplace equation for electric potential is solved by finite element method. The numerical model incorporates mapped infinite element to account for potential decay far away from the LED structure and finite element model developed for boundary condition at semiconductor-air interface in the mesh opening. Simulation results demonstrate the effect of the mesh geometrical parameters on the total output power.

Modeling of light-emitting diode with top p-electrode patterned as a mesh

Light-emitting diodes (LEDs) with patterned metal electrode to the top p-semiconductor layer resulting in enhanced light extraction are studied. Analytical model which includes an efficient procedure for numerical calculation of light extraction under nonuniform current injection caused by contact patterning is developed and used for modeling of two-dimensional spatial distributions of potential, injected current and output optical power.

Study of fringing effects in multi-cantilever HEMT-based resonant MEMS

An analytical model of a resonant micro-electromechanical system (MEMS) with a high-electron mobility transistor (HEMT)-like structure and an array of resonant cantilevers over its two-dimensional electron gas (2DEG) channel is developed. To account for impact of fringing, spatial distributions of the electric field and sheet electron density at the surface of the HEMT channel are calculated in parametric form. Resistance of the 2DEG channel and frequency-dependent ac amplitude of the source–drain current are derived. The developed model allows evaluation of impact of fringing electric field on output source–drain current for any different number of cantilevers in the array at different spacing between them and can be used for device optimization.