Study of amplified emission in polycrystalline ZnO below characteristic temperature

TL;DR

This study investigates amplified emission phenomena in polycrystalline ZnO below 100K, revealing temperature-dependent excitonic emissions, their shifts, and the conditions for amplification, with implications for optoelectronic applications.

Contribution

It provides detailed experimental insights into excitonic emissions and amplification thresholds in ZnO at low temperatures, highlighting temperature effects on emission properties and thresholds.

Findings

Amplified emission observed below 100K in ZnO.

Exciton emission peaks shift with excitation intensity and temperature.

Threshold excitation decreases exponentially with temperature up to 100K.

Abstract

We report on amplified emission in polycrystalline ZnO below 100K. At 6K emission is due to free exciton FXn=1 A (3.378 eV), bound exciton D1XA (3.347 eV), donor acceptor pair DAP (3.275 eV) and longitudinal phonon replica of free excitons (FXn=1 A -mLO, m= 1,2,3) respectively. Peak intensity of D1XA and FXn=1 A -1LO transition increases non-linearly with increase of excitation intensity due to exciton-exciton scattering. Peak position of D1XA shows red shift while FXn=1 A -1LO shows blue shift with increase of excitation intensity. Fraction of exciton taking part in emission process and radiative lifetime of exciton decreases with decrease of temperature .Threshold value of excitation for D1XA decreases exponentially with decrease of temperature upto 100K. Whereas, below 100K no functional behaviour is observed. Threshold for FXn=1A-1LO emission was observed up to 75K, at higher temperature it is mixed with D1XA. Time delayed photoluminescence measurement reveals that amplified emission decay faster than spontaneous emission.