# Effects of Different InGaN/GaN Electron Emission Layers/Interlayers on Performance of a UV-A LED
## 3 Results and Discussion
In practice, the ESB shows a stronger effect on step-edge at low growth temperatures [19]. When GaN layers are grown at the same temperature, TEGa is easily decomposed at a relatively lower growth temperature than TMGa. Therefore, the ES effect occurs easily in the GaN layer grown with TEGa compared to one grown with TMGa. To investigate the optical properties of the epi-structure grown on EELs/ILs/n-GaN/u-GaN on substrate, we measured the PL of three samples as shown in Figure 3. Two separate emissions at 360 nm and 365 nm are clearly distinguished for all samples and related to emission from GaN and InGaN, respectively. EI-UVLED III with GaN barriers grown by the TEGa source has a PL intensity 1.2 times higher than EI-UVLED I consisting of EELs/ILs with GaN barriers grown with the TMGa source. The improvement of PL intensity in EI-UVLED III was attributed to the optimized growth condition, due to the improved crystalline quality resulting from insertion of the GaN barrier with the TEGa layer. For more detailed evaluations of the GaN barrier layer grown with different MO precursors, the GaN barrier layer was sequentially formed on the same u-GaN/sapphire template with a TMGa or TEGa MO source, and the PL properties of the grown GaN layers were compared as shown in Figure 4a. The GaN layer grown with TEGa has a near-band-edge PL intensity two times higher than the GaN layer grown with TMGa. The green to yellow emission PL peaks of the GaN layer represent the incorporated defects. The spectrum was converted to a logarithmic scale to confirm the defects related to the green and yellow emissions around 500 nm to 600 nm. The green to yellow emissions of GaN are dominated by deep level emission, showing point defects such as Ga-vacancy-related V\({}_{\text{Ga}}\)-O\({}_{\text{N}}\)  
Figure 2: Atomic force microscopy (AFM) surface scan and line profiles of GaN/EELs/ILs for (**a**) EI-UVLED I, (**b**) EI-UVLED II, and (**c**) EI-UVLED III. Width and height are denoted in the figures. complex and edge dislocation density [20]. The integrated intensity ratios of the yellow luminescence band to the near-band-edge emission (I\({}_{\text{YL}}\)/I\({}_{\text{BE}}\)) are 0.04 and 0.16 for the GaN layer grown with TEGa or TMGa, respectively, as shown in Figure 4b. The deep acceptor-related emissions for I\({}_{\text{YL}}\) originated from the Ga-vacancy-related (V\({}_{\text{Ga}}\)) native defects or its complexes with O and H in GaN thin films. Formation of point defects induced non radiative recombination centers that decreased PL intensity. Furthermore, the spectra show full width at half-maximum (FWHMs) peak emission of 8.2 and 11.6 nm at 360 nm of GaN grown by TEGa and TMGa, respectively. The PL analysis confirmed that the GaN layer grown with a TEGa source had better optical properties with relatively fewer defects than that grown with TMGa. Crystalline quality and interface of our epitaxial structures were evaluated by HR-XRD. Figure 5a,b shows the HR-XRD rocking curves for the (002)- and (102)-plane reflections, respectively, obtained from the UVLED full structures grown on the Al\({}_{2}\)O\({}_{3}\) substrates. The FWHMs of the (002) XRD rocking curve (XRC) of GaN with conditions of UVLED -I, -II, -III are 272, 266, and 250 arcsec, respectively. The FWHMs of the (102) rocking curve of the GaN layer with conditions of UVLED-I, -II, -III are 325, 310, and 285 arcsec, respectively. The FWHMs of rocking curves from epi-structures consisting of the GaN barriers grown with TEGa are narrower than those of the sample grown with TMGa, indicating superior crystal quality of GaN epi grown with TEGa. Generally, the rocking curve's FWHMs of (102) and (002) planes are very sensitive to edge and scre  
Figure 4: (**a**) PL spectra gathered from un-doped GaN grown with trimethylgallium (TMGa) and triethylgallium (TEGa) and (**b**) the spectra on a logarithmic scale. Figure 3: Photoluminescence (PL) spectra obtained from three samples with different GaN barrier growth conditions in EELs/ILs. respectively [21].