InGaN/GaN MQW

Fig. 2. High resolution XRD patterns of InGaN/ GaN MQW as a function of flow rate of TMIn.

Fig. 3. Forward (top) and reverse (bottom) voltages of InGaN/GaN MQW LED with and without annealing after etching as a function of ICP source power.

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... 

High-temperature SE was also observed in MOCVD-grown InGaN/GaN MQWs up to 575 K [23], The number of periods of the MQWs was 12, the nominal well and barrier layer thicknesses were 30 and 45 A,... 

FIGURE 3 Emission spectra from an InGaN/GaN MQW sample for two different temperatures ... 

FIGURE 3 Room temperature C W operating characteristics of a facet coated InGaN/GaN MQW laser grown on SiC showing (a) the spectrum above threshold and (b) the L-I curve. 

OPTICAL GAIN SPECTRA AND LASER ACTION OF InGaN/GaN MQWs GROWN ON SILICON AT PUMPING BY FEMTOSECOND PULSES... 

Optical gain spectra and laser action of InGaN/GaN MQWs grown on silicon at pumping by femtosecond pulses. 

Laser action without any visible degradation was obtained in the InGaN/GaN MQW heterostmctures up to T = 585 K. The laser spectra at low / xc consist of one very narrow line with the lowest FWHM of 0.04 nm. All lasers had well pronounced threshold input-output characteristics. The external differential quantum efficiency of the laser operating at 452 nm for TE polarisation amounts to the value of 77 = 3%. The maximum total energy and power per pulse from both facets were 300 nJ and 40 W, correspondingly, at room temperature for lias = 452 nm. 

Research results on optical, laser, electroluminescent and structural properties of InGaN/GaN MQW heterostructures grown on silicon substrates are presented. Concentration of In in QWs and the thickness of the layers were estimated from X-ray diffraction measurements. For the first time, laser action under optical excitation was obtained for InxGai.xN/GaN/Si MQW heterostructures (x = 0.151, /.hr = 40-80 kW/cm at room temperature, T ax = 630 K, P=10 W, =80 nJ). 

InGaN/GaN MQW structures grown on silicon were also studied by structural measurements. The X-ray diffraction pattern taken around GaN (0002) of the sample depicted in Fig. 3 is an evidence of its good quality. The simulation based on the dynamical theory of X-ray scattering shows a reasonable match to the experimental d ata. This simulation yielded the thickness and c ompositions o f the MQW (3.4 nm Ino,i5iGao.849N + 3.9 nm GaN). For the parameter refinement, the relaxation status of the buffer layers was taken into account. 

Figure 1. PL spectra positions (a) and PL efficiencies (b) of an InGaN/GaN MQW heterostructure grown on silicon as functions of / . (1) and temperature (2, 3).

Figure 2. RT lasing (1) and gain (2) spectra of an InGaN/GaN MQW heterostructure relatively to its PLE...

Figure 3. Experimental (0002) XRD data and simulated curves on InGaN/GaN MQW grown on sapphire (a) and on silicon (c) as well as RT lasing spectra of the same samples (b).

It is shown that spontaneous emission, gain and lasing in InGaN/GaN MQW heterostructures grown on silicon occur due to radiative recombination of carriers spatially localized on potential minima in In-rich clusters. 

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