Intensive measures of luminescence in GaN/InGaN heterostructures.

Jui-Ju Hsiao,Ya-Fen Wu,Hung-Ing Chen,Jen-Cheng Wang,Joe-Air Jiang,Tzer-En Nee,Yi-Jen Huang,Manikoth Shaijumon

doi:10.1371/journal.pone.0222928

Abstract

The intensive measures of luminescence in a GaN/InGaN multiple quantum well system are used to examine the thermodynamics and phenomenological structure. The radiative /nonradiative transitions along with absorbed or emitted phonons that occur between the different quantum states of the electrons and holes associated with these processes make the quantum efficiency of a semiconductor nanosystem in an equilibrium state an extensive property. It has long been recognized that tuning of the indium (In) composition in InGaN interlayers gives the potential to obtain a spectrum in the near-infrared to near-ultraviolet spectral range. The thermodynamic intensive properties, including the Debye temperature, carrier temperature, and junction temperature, are the most appropriate metrics to describe the optical-related interactions inherent in a given heterostructure and so can be used as the state variables for understanding the quantum exchange behaviors. The energetic features of the quantum processes are characterized based on analysis of the intensive parameters as determined by means of electroluminescence (EL) and photoluminescence (PL) spectroscopy and current-voltage measurement and then correlated with the designed InGaN/GaN microstructures. According to the McCumber-Sturge theory, the EL and PL Debye temperatures obtained experimentally signal the strength of the electron-phonon and photon-phonon interaction, respectively, while the EL and PL carrier/junction temperatures correspond to the carrier localization. Higher EL Debye temperatures and lower EL carrier/junction temperatures reflect significantly higher luminescence quantum yields, indicative of electron-phonon coupling in the transfer of thermal energy between the confined electrons and the enhancement by excited phonons of heat-assisted emissions. On the other hand, the observation of low luminescence efficiency, corresponding to the lower PL Debye temperatures and higher PL carrier/junction temperatures, is attributed to photon-phonon coupling. These findings are in good accordance to the dependence of the EL and PL quantum efficiency on the In-content of the InGaN/GaN barriers, suggesting that the characteristic Debye and carrier/junction temperatures are intensive parameters useful for assessing the optical properties of a nano-engineered semiconductor heterostructure.

Highlights

Advances in semiconductor nanoscience and nanotechnology will allow for continued rapid progress towards the development of an improved understanding of the fundamental physical principles governing the quantum processes at the nanoscale level [1,2,3]
We found that there was a decrease in the EL thermally-related full width at half maximum (FWHM) with an increase in the InN molar fraction incorporated into the GaN/InGaN interlayers
Thermodynamic intensive parameter analysis of the luminescence characteristics for GaN/ InGaN multiple quantum wells (MQWs) systems subjected to electrical injection and optical excitation was performed

Summary

Introduction

Advances in semiconductor nanoscience and nanotechnology will allow for continued rapid progress towards the development of an improved understanding of the fundamental physical principles governing the quantum processes at the nanoscale level [1,2,3]. Both reduced dimensionality and device scaling lead to increased problems of heat management in heterostructures. The phonon-related interactions associated with electrons and photons become important design issues for a wide range of technologies, such as for microwave devices, high-k devices, metal-oxide-semiconductor field-effect transistors (MOSFETs) with high-k gate oxides, solar cells, light-emitting diodes, and laser diodes [4,5,6,7,8]. To corroborate the robustness of our proposed scheme, we characterize the dependence of the quantum efficiency of EL and PL on the In molar fraction in the InGaN/GaN interlayers

Experiments

Results and discussion

Conclusions