Investigation of AlGaN/GaN high electron mobility transistors on Silicon (111) substrates employing multi-stacked strained layer superlattice structures

Highly Transparent p‐AlGaN‐Based (326–341 nm)‐Band Ultraviolet‐A Light‐Emitting Diodes on AlN Templates: Recent Advances and Perspectives

“…By using XRCs data, the screw-type TDs (ρ s ) % 7.7 Â 10 8 cm À2 and edge-type TDs (ρ e ) % 5.3 Â 10 9 cm À2 in the n-AlGaN ESL of sample-Ref, were estimated by following the method given in refs. [50,51] The total-TDDs %3 Â 10 9 cm À2 in n-AlGaN ESL of sample-Ref were also measured by HR-STEM. Based on the PL intensity at RT as well as at 77 K in sample-Ref, the relative IQE in the UVA MQWs was estimated to be 30%, as shown in Figure 2D.…”

“…Based on the XRCs data, the estimated screw‐type TDs ( ρ s ) ≈ 7.7 × 10 8 cm −2 and edge‐type TDs ( ρ e ) ≈ 5.3 × 10 9 cm −2 respectively, in the n‐AlGaN ESL of sample‐Ref [ 18 ] are reduced to 5 × 10 8 and 1 × 10 9 cm −2 in sample‐WP, using the estimation method given elsewhere. [ 50,51 ] There is deep relationship between TDs and IQE in the MQWs. [ 42,43 ] The IQE of sample‐WP was also measured by the standard method given in ref., [ 22 ] shown in Figure 5E,F.…”

“…[ 18 ] Previously, an AlGaN/GaN superlattices layer (SLs) was introduced instead of strained AlGaN/AlN SLs structure, which revealed a remarkable reduction of pit density and TD density in the grown epilayer. [ 51 ] As a result, the device performance, such as carrier mobility and sheet carrier density at RT in AlGaN/GaN HEMTs were greatly improved. [ 51 ] In this work, the influence of the 428 nm‐thick and pure n‐AlGaN SLs structure as a BL with 60–70 periods, on the suppression of TDs and on the enhancement of IQE and EQE in a UVA emitter (sample‐C, sample‐II, and sample‐II) were reinvestigated, by following route‐02 of crystal growth, shown in Figure A–F.…”

“…such as EL or PL peak broadening has been widely investigated by following to the most relevant references. [18][19][20][21][25][26][27][28][29][30]50,51] The narrow-band (NB) % 7 nm EL emission spectra at 341 nm emission using Ni/Au p-electrode in the SLs-based UVA LED (sample-III) under different current drives were investigated, and single peak operation were confirmed, as shown in the inset of Figure 9C. Previously, it was observed that the strain-relaxation condition in the n-AlGaN ESL may not only generate the extended defects and crystal irregularities in the UVA MQWs, but it can also excite to growth of 3D mode in the AlGaN materials.…”

“…The XRCs of the n-AlGaN ESL in the sample-WP were also characterized, where the FWHM value of the XRCs for (0002) and (10-12) planes, respectively, were successfully reduced from our previous value of 595 and 793 arcsec in sample-Ref,[18] to 480 and 500 arcsec, by using three-stacking layers of Al-graded n-AlGaN BLs and highly relaxed n-AlGaN ESL underneath the UVA MQWs (sample-WP), shown in Figure5C,D. Based on the XRCs data, the estimated screw-type TDs (ρ s ) % 7.7 Â 10 8 cm À2 and edge-type TDs (ρ e ) % 5.3 Â 10 9 cm À2 respectively, in the n-AlGaN ESL of sample-Ref[18] are reduced to 5 Â 10 8 and 1 Â 10 9 cm À2 in sample-WP, using the estimation method given elsewhere [50,51]. There is deep relationship between TDs and IQE in the MQWs [42,43].…”