Vertical cavity surface emitting lasers utilizing native oxide mirrors and buried tunnel contact junctions

Abstract

Vertical cavity surface emitting lasers ͑VCSELs͒ are demonstrated with high-index-contrast native-oxide-based (Al x O y) distributed Bragg reflectors ͑DBRs͒ on both sides of a ''2'' cavity, thus creating a compact ͑thin, ϳ2.8 m͒ laser structure. Selective oxidation of high Al composition Al x Ga 1Ϫx As layers yields a structure with a four period upper Al x O y /GaAs DBR, a 5.5 period lower Al x O y /GaAs DBR, and a buried oxide current aperture. A reverse-biased tunnel contact junction provides hole injection via lateral electron current between the upper DBR and the oxide aperture layer. These VCSELs operate with submilliampere thresholds, high spontaneous efficiencies, and excellent polarization control.

Observation of the Purcell effect in high-index-contrast micropillars

“…A Bragg mirror consisting of alternate layers of GaAs and AlOx gives a reflectivity of ~ 15% at each interface. Consequently, several investigations have been carried out into the use of AlOx in Bragg mirrors and cavities [7][8][9][10][11], concentrating on vertical-emission light sources with relatively large lateral dimensions.…”

“…Although 3.0 μm diameter pillars have variable mode wavelengths and Q, it was possible to identify a number of pillars with quantum dot exciton (X) emissionlines spectrally close to the HE 11 mode. As these pillars have a diameter several times the mode wavelength we expect a well collimated emission pattern from the HE11…”

Blue and Near-Ultraviolet Vertical-Cavity Surface-Emitting Lasers

“…Second, and more important from the viewpoint of both expanded design flexibility and easier device processing, is the recently developed (Esaki) tunnel junction based on a thin, heavily doped p ϩϩ /n ϩϩ InGaN/GaN bilayer. 15 In general, the tunnel-junction concept, already well utilized in GaAs-based optoelectronic devices, 16 offers a versatile new heterostructured building block for nitride optoelectronic devices. We focus on its adaptation into vertical-cavity lasers and other light-emitters in the remainder of this article.…”

Microstructure and wet oxidation of low-temperature-grown amorphous (Al/Ga,As)

“…Since its discovery in 1990, 1 the robust native oxide formed by water-vapor oxidation of crystalline Al-bearing compound semiconductors has been used in many applications ranging from electronic 2,3 to optical devices. [4][5][6][7][8] The oxide of AlGaAs compounds via wet oxidation is mechanically robust and chemically stable. 1 It has been used as the gate oxide for III-V-based field-effect transistors ͑FETs͒, though only depletion-mode devices were reported.…”

“…The nonconducting nature allows the oxide to confine electrical current, 11 and the selective lateral oxidation with respect to Al concentration facilitates the formation of distributed Bragg reflectors ͑DBRs͒ for vertical-cavity surface-emitting lasers ͑VCSELs͒. [6][7][8] A large reduction in the refractive index results ͑from 3.2 to 1.6͒ when AlAs is oxidized. The larger difference of refractive indices between the Al oxide and GaAs achieved by laterally oxidizing the initial AlAs/GaAs pair permits the formation of effective DBR mirrors without the need for a large number of pairs.…”