Time-Resolved Photoluminescence Studies of GaN

Since GaN materials contain a high density of extended defects (10 - 1010 cm 2), it is expected that the carrier and exciton recombination dynamics vary from sample to sample. Studies have revealed that the exciton lifetime is correlated with the yellow emission line at about 2.2 eV the stronger the yellow 

FIGURE 2 PL emission spectra of GaN/AlxGai.xN MQWs and GaN epilayer measured at 10 K. 

FIGURE 3 PL temporal responses measured at the spectral peak positions for MBE and MOCVD samples GaN and InxGai.xN epilayers, GaN/AlxGai.xN and InxGai.xN/GaN MQWs. 

FIGURE 4 Temperature dependence of the recombination lifetimes of the excitonic transitions in Ill-nitride epilayers and MQWs. 

Carrier and exciton dynamics in InGaN/GaN MQWs have also been studied at a high optical pumping power [34], At 7 K, a radiative decay lifetime of 250 ps was observed for the dominant transition at a generated carrier density of 1012/cm2. The time-resolved measurement showed that the decay of PL has a bimolecular recombination characteristic. At room temperature, the carrier recombination was found to be dominated by non-radiative processes with a measured lifetime of 130 ps. Well width dependence of carrier and exciton dynamics in InGaN/GaN MQWs has also been measured [35]. The dominant radiative recombination at room temperature was attributed to the band-to-band transition. Combined with an absolute internal quantum efficiency measurement, a lower limit of 4 x 10 9 cm3/s on the bimolecular radiative recombination coefficient B was obtained. At low temperatures, the carrier 

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A3.5 Time-resolved photoluminescence studies of GaN A3.6 Persistent photoconductivity in GaN A3.7 Electrical transport in wurtzite and zincblende GaN A3.8 Characterisation of III-V nitrides by capacitance transient spectroscopy... 

The spontaneous emission of C-plane (In,Ga)N quantum wells is determined by both the electron-hole wavefunctions separation due to the built-in internal electrostatic field (quantum-confined Stark effect) and exciton local-i2ation caused by potential fluctuations [71-74]. The reali2ation of M-plane (In,Ga)N/GaN MQWs allows us to investigate the impact of exciton locali2ation on radiative recombination without the influence of internal electrostatic fields. To study the recombination mechanism of M-plane (In,Ga)N/GaN MQWs, continuous-wave photoluminescence (cw-PL) spectroscopy and time-resolved (TR) PL were carried out. 

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