Dopants concentration effect on gallium arsenide and gallium nitride-based homojunction LED epi-layers

Abstract

This work reports the effect of doping on the energy-band structure of homojunction light-emitting diode (LED) epitaxial layers. The research correlates the resultant values of bandgap energy and its depletion region, which are then applied to the luminescence spectrum of the light-emitting diode. The energy-band structure is simulated by initializing the various materials’ properties of Gallium Nitride (GaN), including Gallium Arsenide (GaAs), and solving the Poisson’s equation derived from Boltzmann’s Transport equation. The equation is solved by applying the finite difference method and using the Newton-Raphson method. Both materials are compared with different dopant concentrations in the range of 1 x 1018 cm-3 to 1 x 1021 cm-3. Taking the Silicon properties as the controlled variable, the energy-band structure is validated with literature findings. The calculated band gap energy of GaAs shifts from 1.4273 eV to 1.4640 eV, and for GaN, from 3.3970 eV to 3.4148 eV. The bandgap energy increases with the proportion to the doping concentration increments. However, when obtaining the epitaxial layer’s active 1-D spatial regions for GaAs and GaN, it reduces from (1.5700x10-1μm – 7.5000x10-3μm) and from (1.8450x10-1μm – 8.5000x10-3μm) x 1 μm2 respectively. The findings show that doping concentration is saturated at a certain threshold, which provides a less significant impact on the semiconductor energy-band structure. Thus, the numerical system determines the LED output spectrum and the threshold values for bandgap energy. The analyzed bandgap thresholds are obtained as 1.440eV for GaAs and 3.403eV for GaN at dopants’ concentrations of 2.951x1019cm-3 and 4.467x1019cm-3, respectively. The peak intensity wavelengths are obtained as 363.17nm for GaN and 845.7nm for GaAs.