Investigation of the electroluminescence spectrum shift of InGaN/GaN multiple quantum well light-emitting diodes under direct and pulsed currents

Abstract

Electroluminescence (EL) spectra of InGaN/GaN multiple quantum well light emitting diodes with different piezoelectric polarization fields were investigated under pulsed and direct currents. We find a positive correlation between the piezoelectric polarization field and the thermally induced red-shift of the EL spectra at high direct currents above 25 A/cm2. Under pulsed current, when thermal effects are negligible, a non-uniform EL spectrum blue-shift rate as a function of injection level is observed and compared with numerical results obtained by both self-consistent and non-self-consistent K·P methods. We conclude that the screening effect is positively related to the piezoelectric polarization field, but the band filling-induced blue-shift is almost independent from the piezoelectric field. The electrostatic fields induced by free carriers in the quantum wells increase rapidly with current but tend to saturate at higher injection where the band filling effect becomes the dominant mechanism for the blue-shift. Finally, at high injection above 30 A/cm2, an increase in Auger recombination and carrier leakage holds the spectral peaks almost constant in position.

InGaN stress compensation layers in InGaN/GaN blue LEDs with step graded electron injectors

“…For LED A the peak wavelength is shifted from 446.8 to 443.5 nm (by 21 meV), and LED B that has SCL exhibits a blue-shift from 442.0 nm to 440.3 nm (by 11 meV). This blue-shift can be a result of QCSE screening as well as band filling [10,28,45]. We emphasize that blue-shift with increasing injection in LED A is twice that in LED B, which suggests smaller strain and QCSE in LED B [45].…”

“…With increasing current injection beyond 150 mA, EL peaks red-shift from 443.5 nm to 444.5 nm (by 6.3 meV) and from 440.3 nm to 441.6 nm (by 8.3 meV) for LEDs A and B, respectively. This red-shift can be attributed to Joule heating of dies, which increases the dispersion of the carrier distribution, and to bandgap renormalization caused by high carrier density in the active region [10,28,45].…”

Straightforward electrical measurement of forward-voltage to investigate thermal effects in InGaN/GaN high-brightness light-emitting diodes

“…The DAQ voltmeter has a sampling rate of 20 000 samples/s giving a time resolution of 50 ls for the instrument. 17,19 Considering this, we find that V f can be accurately established within 3 ms after switching to low current, allowing the setup time to pass the Gibbs overshoot while preceding significant cooling in the active region.…”

“…1(a), can be used to calculate the junction temperature for the LED. 7,[17][18][19] In addition, the blue shift is expected from carrier-induced screening of the built-in field within the (0001)-oriented III-nitride quantum wells. Delays in the current source upon changing from high to low drive conditions become the limiting factor in the junction temperature determination.…”

GaN-Based Enhancement-Mode Metal–Oxide–Semiconductor High-Electron Mobility Transistors Using LiNbO3Ferroelectric Insulator on Gate-Recessed Structure

“…I N THE past decades, in view of the significant progress of epitaxial growth and fabrication techniques [1], [2], gallium nitride (GaN)-based semiconductors have been widely used in electronic devices [3], [4], optoelectronic devices [5], [6], and sensors [7], [8]. Among the GaN-based epitaxial structure used in devices, the AlGaN/GaN-based heterojunction was widely explored due to its inherent advantages of the high electron mobility of the 2-D electron gas .…”