Abstract
Transparent conductive layers (TCLs) deposited on a GaP window layer were used to fabricate high-brightness p-side-up thin-film AlGaInP light-emitting diodes (LEDs) by the twice wafer-transfer technique. Indium tin oxide (ITO) and aluminum-doped zinc oxide (AZO) were used as TCLs for comparison. The TCLs improved droop of external quantum efficiencies (EQE) of LEDs and junction temperature, which result in increasing the light output power and thermal stability of the LEDs. The droop efficiency of Ref-LED, ITO-LED and AZO-LED were 64%, 27% and 15%, respectively. The junction temperature of ITO-LED and AZO-LED reduced to 49.3 and 39.6 °C at an injection current of 700 mA compared with that (80.8 °C) of Ref-LED. The LEDs with AZO layers exhibited the most excellent LED performance. The emission wavelength shifts of LEDs without a TCL, with an ITO layer, and with an AZO layer were 17, 8, and 3 nm, respectively, when the injection current was increased from 20 to 1000 mA. The above results are promising for the development of AZO thin films to replace ITO thin films for AlGaInP LED applications.
Highlights
Quaternary (Al1-xGax)0.5In0.5P-based light-emitting diodes (LEDs) with red and yellow/green spectra have received considerable attention
Most photons are trapped inside the LED chip in a guided mode, which results from the large difference in the refractive indices between the semiconductor and epoxy for the packaged AlGaInP LEDs
To evaluate the contact resistance of transparent conductive layers (TCLs) contacted to p-GaP:C, the aluminum-doped zinc oxide (AZO) thin film was annealed at 350°C for 1 minute under N2 ambient and indium tin oxide (ITO) thin film without post annealing for comparison with AuBe/Au deposited on a p-GaP:C layer using 550°C annealing for 30 seconds
Summary
Quaternary (Al1-xGax)0.5In0.5P-based light-emitting diodes (LEDs) with red and yellow/green spectra have received considerable attention. Indium tin oxide (ITO) as a TCL has been proven to be one of the most promising materials for enhancing light extraction in AlGaInP-based LEDs because of its excellent conductivity and optical transparency in the visible wavelength range [7]. It is chemically unstable, toxic, rare, and expensive. AlGaInP LEDs with a thin carbon-doped GaP cap layer were transferred onto a Si substrate with mirror structure (i.e. Ag-reflector) using the twice wafer-transfer technique to construct p-side-up thin-film AlGaInP LEDs with vertical metal contacts. The electrical properties of p-side-up thin-film AlGaInP LEDs with ITO and AZO thin films used as current spreading layers to enhance the light extraction efficiency are compared and described in detail
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
