Analysis and electrical characterization of blue light emitting diode

An analytical model for the structures commonly employed for the fabrication of blue light emitting diodes (LEDs) based on AlGaN/GaN/AlGaN double heterojunctions has been developed. Insight gained from the analysis was employed to interpret observed current-voltage and capacitance-voltage characteristics obtained from commercially available blue LEDs. These diodes are highly non-ideal with several regimes characterized by high values of the ideality factor ranging from 2.90 - 6.76 indicating that the recombination process cannot be described by the Shockley-Read-Hall mechanism. Logarithmic plots of the forward characteristics indicate a space-charge-limited-current conduction through the active region of the diodes. Observed changes in slope of these logarithmic plots are representative of a high density of "deep-level states" in the active region of the diodes. An analysis of these characteristics yielded a density of deep-level states of ∼2 × 10¹⁷/cm³. Deep-level states concentrations were also determined from capacitance-voltage measurements; these were in good agreement with concentrations determined from current-voltage measurements. Recombination lifetimes were extracted from diode reverse recovery storage time measurements.