Abstract
In conventional emitting devices, the mobility of electron is much higher than that of hole, which increases the non-recombination rate. To generate slow electrons, we demonstrate an electron retarding n-electrode (ERN) on the n-GaN layer of InGaN blue light emitting diode (LED), making more efficient radiation emission. Transparent conductive oxides are estimated to be more suitable for ERN materials. However, for ERN materials used in InGaN LEDs, three requirements should be satisfied, i.e., Ohmic contact to n-GaN, dilute magnetic doping, and good electrical conductivity. The pulsed-laser deposited cobalt-doped ZnO film prepared at 400 °C was chosen as the ERN. The electron retarding of 120-nm-thick ERN/n-GaN reached 19.9% compared to the n-GaN. The output powers (@350 mA) of LEDs with and without the ERN were 246.7 and 212.9 mW, while their wall-plug efficiencies were 18.2% and 15.1%, respectively. Moreover, owing to the efficient filling of electrons in the quantum wells by inserting the ERN, the bandgap of quantum wells was enlarged, inducing the blue-shift in the emission wavelength of LED. The slow electron generated from the ERN technique paves the way to solve the problem of large difference between electron and hole velocities and improve the optoelectronic performance of emitting devices.
Highlights
With the invention of emitting devices, such as laser diodes (LDs) and light emitting diodes (LEDs), the human life becomes more convenient[1,2,3]
To produce the slow electrons in the emitting device, we have proposed the electron retarding n-electrode (ERN) on the n-GaN layer to enhance the optoelectronic performance of nitride LEDs
Based on the simulated results, the internal quantum efficiency (IQE) of blue LED can be increased from 60.6% to 63.67% with increasing the electron retarding ratio from 0% to 80%
Summary
With the invention of emitting devices, such as laser diodes (LDs) and light emitting diodes (LEDs), the human life becomes more convenient[1,2,3]. Even though the emission efficiency of devices can be improved efficiently, an essential problem in these emitting devices, i.e., the excessively large velocity (mobility) difference between electron and hole carriers, is still not overcome. The velocity of electron in a conventional blue InGaN LED is approximately 26 times faster than that of hole This large difference between electron and hole velocities would increase the non-recombination rate of the device, degrading its emission performance[10,11]. Via the deposition of CZO-ERN on n-GaN, the electron mobility becomes slower, making more efficient radiation emission on nitride LEDs. Most importantly, the problem of the excessively large velocity difference between electron and hole carriers occurred in various emitting devices can be successfully solved by introducing the slow electrons
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