Optical modes within III-nitride multiple quantum well microdisk cavities

Abstract

Optical resonance modes have been observed in optically pumped microdisk cavities fabricated from 50 Å/50 Å GaN/Al x Ga 1Ϫx N(xϳ0.07) and 45 Å/45 Å In x Ga 1Ϫx N/GaN(xϳ0.15) multiple quantum well structures. Microdisks, approximately 9 m in diameter and regularly spaced every 50 m, were formed by an ion beam etch process. Individual disks were pumped at 300 and 10 K with 290 nm laser pulses focused to a spot size much smaller than the disk diameter. Optical modes corresponding to ͑i͒ the radial mode type with a spacing of 49-51 meV ͑both TE and TM͒ and ͑ii͒ the Whispering Gallery mode with a spacing of 15-16 meV were observed in the GaN microdisk cavities. The spacings of these modes are consistent with those expected for modes within a resonant cavity of cylindrical symmetry, refractive index, and dimensions of the microdisks under investigation. The GaN-based microdisk cavity is compared with its GaAs counterpart and implications regarding future GaN-based microdisk lasers are discussed.

Size dependence of III-nitride microdisk light-emitting diode characteristics

“…[4][5][6] Enhanced quantum efficiency ͑QE͒ and optical resonant modes have been observed in these microcavities. Most recently, we have fabricated electrically pumped InGaN/GaN QW individual -disk LEDs with a diameter of about 10 m and it was shown that the QE was higher in -disk LEDs than in the conventional broad-area LEDs.…”

Observation of high Q resonant modes in optically pumped GaN/InGaN microdisks fabricated using photoelectrochemical etching

“…These modes were observed at an excitation power density of 4.82 kW/cm 2 , which is over 5 times lower than the power densities previously reported for a GaN-based microdisks [4,5]. However, the microdisks exhibit a large background of optical noise.…”

“…However, to date, the most notable GaN-based microdisk results have been from structures which use the lower refractive index of the sapphire substrate for vertical optical confinement and a single dry etch step to form disks for lateral optical confinement. These devices have shown rather broad, low Q emission and required high pump power densities (25 kW/cm 2 average power from a picosecond excitation source) [4,5]. Using bandgap selective photoelectrochemical (PEC) etching [6,7], we have fabricated mushroom-shaped GaN disks with InGaN active regions which exhibit high Q values from 1700-2700.…”

Directional emission from a microdisk resonator caused by a linear defect

“…Nitride-based lasers operating at λ ≈ 0.4µm [19][20][21] have much higher M -values (200 < ∼ M < ∼ 600) and n ≈ 2.8. This yields FWHM of 64…”