Effect of crystal-field split-off hole and heavy-hole bands crossover on gain characteristics of high Al-content AlGaN quantum well lasers

Abstract

The optical gain characteristics of high Al-content AlGaN quantum wells (QWs) are analyzed for deep UV lasers. The effect of crystal-field split-off hole (CH) and heavy-hole (HH) bands crossover on the gain characteristics of AlGaN QW with AlN barriers is analyzed. Attributing to the strong transition between conduction–CH bands, the TM spontaneous emission recombination rate is enhanced significantly for high Al-content AlGaN QWs. Large TM-polarized material gain is shown as achievable for high Al-content AlGaN QWs, which indicates the feasibility of TM lasing for lasers emitting at ∼220–230 nm.

Ultraviolet optoelectronic devices based on AIGaN alloys grown by molecular beam epitaxy

“…[130][131][132][133] Since the wells in our structure are very thin, it is reasonable that the TE polarization is still predominant.…”

Demonstration of transverse-magnetic deep-ultraviolet stimulated emission from AlGaN multiple-quantum-well lasers grown on a sapphire substrate

“…The small wavelength variation of $4 nm in the emission wavelengths of these lasers are due to lateral wafer inhomogeneities, which can include variation of strain state, composition, layer thickness, and carrier density. [15][16][17][18][19] As the excitation power density increased, the spectral linewidth narrowed significantly and reached FWHM values of 1.4-2.3 nm at respective maximum excitation power density, which indicated stimulated emission. 2,3 The laser thresholds were estimated to be 280, 250, and 290 kW/cm 2 for the 239-nm, 242-nm, and 243-nm lasers, respectively.…”

“…9,20,21 This can be attributed to the dramatic change in the ratio of TE-to-TM gain coefficients for the DUV AlGaN MQW lasers in the vicinity of TE-TM switch. 17 In summary, TM-dominant DUV stimulated emission from photo-pumped AlGaN MQW lasers grown by MOCVD on sapphire substrates were demonstrated at RT. TMdominant stimulated emission was observed at 239, 242, and 243 nm with low thresholds of less than 300 kW/cm 2 .…”

Investigation of GaN-based dual-wavelength light-emitting diodes with p-type barriers and vertically stacked quantum wells

“…The band-offset ratio is assumed to be 0.7/0.3 for both InGaN and AlGaN [28] . Note that the surface charges could be screened due to the defects inside the device, and that the amount obtained from the experimental measurement is usually smaller than that obtained by theoretical calculation with the self-consistent model [29,30] . In this letter, we assume the screen loss is 60%, and we take 40% of the calculated surface charges to match the experimental results [31] .…”