Improved Vertical Carrier Transport for Green III-Nitride LEDs Using (In,Ga) N Alloy Quantum Barriers
Journal
Physical Review Applied
Journal Volume
17
Journal Issue
5
Date Issued
2022
Author(s)
Abstract
We report on experimental and simulation-based results using (In,Ga)N alloy quantum barriers in c-plane green light-emitting diode (LED) structures as a means to improve vertical carrier transport and reduce forward voltage (VF). Three-dimensional device simulations that include random alloy fluctuations are used to understand carrier behavior in a disordered potential. The simulated current density-voltage (J-V) characteristics and modified electron-hole overlap |Fmod|2 indicate that increasing the indium fraction in the (In,Ga)N quantum barriers leads to a reduced polarization discontinuity at the interface between the quantum barrier and quantum well, thereby reducing VF and improving |Fmod|2. Maps of electron and hole current through the device show a relatively homogenous distribution in the XY plane for structures using GaN quantum barriers; in contrast, preferential pathways for vertical transport are identified in structures with (In,Ga)N barriers as regions of high and low current. A positive correlation between hole (electron) current in the p-side (n-side) barrier and indium fraction reveals that preferential pathways exist in regions of high indium content. Furthermore, a negative correlation between the strain ϵzz and indium fraction shows that high indium content regions have reduced strain-induced piezoelectric polarization in the Z direction due to the mechanical constraint of the surrounding lower indium content regions. Experimentally, multiple quantum well green LEDs with (In,Ga)N quantum barriers exhibit lower VF and blue-shifted wavelengths relative to LEDs with GaN quantum barriers, consistent with simulation data. These results can be used to inform heterostructure design of low VF, long-wavelength LEDs and provide important insight into the nature of carrier transport in III-nitride alloy materials. © 2022 American Physical Society.
Other Subjects
Carrier transport; Gallium nitride; III-V semiconductors; Indium; Light emitting diodes; Polarization; Quantum chemistry; Semiconductor alloys; Carriers transport; Diode structure; Electron currents; Forward voltage; Green light emitting diodes; High indium contents; III-Nitride; Indium fractions; Preferential pathways; Quantum barriers; Semiconductor quantum wells
Type
journal article