H. Jeon

Blue‐green injection laser diodes in (Zn,Cd)Se/ZnSe quantum wells

Laser diode action in the blue‐green has been observed from (Zn,Cd)Se quantum wells within ZnSe/Zn(S,Se) p‐n heterojunctions up to 250 K. Operation is reported for two different configurations for which the GaAs substrate serves either as the n‐ or p‐type injecting contact. In pulsed operation, output powers exceeding 0.6 W have been measured in devices prepared on both n‐type and p‐type GaAs epitaxial buffer layers and substrates.

Graded band gap ohmic contact to p-ZnSe

We describe a low‐resistance quasi‐ohmic contact to p‐ZnSe which involves the injection of holes from heavily doped ZnTe into ZnSe via a Zn(Se,Te) pseudograded band gap region. The specific contact resistance is measured to be in the range of 2–8×10−3 Ωu2009cm2. The graded heterostructure scheme is incorporated as an efficient injector of holes for laser diode and light emitting diode devices, demonstrating the usefulness of this new contact scheme at actual device current densities.

Blue and green diode lasers in ZnSe‐based quantum wells

Laser diode operation has been obtained from (Zn,Cd)Se/ZnSe and (Zn,Cd)Se/Zn(S,Se) quantum well structures in the blue and the green. The devices, prepared on p‐ and n‐type (In,Ga)As or GaAs buffer layers for lattice matching purposes to control the defect density, have been operated at near‐room‐temperature conditions and briefly at room temperature with uncoated end facets. Quasi‐continuous wave operation has been obtained at T=77 K.

Room‐temperature blue lasing action in (Zn,Cd)Se/ZnSe optically pumped multiple quantum well structures on lattice‐matched (Ga,In)As substrates

We report on studies of optically pumped laser action in (Zn,Cd)Se/ZnSe multiple quantum well structures prepared by molecular beam epitaxy on lattice‐matched bulk (Ga,In)As substrates. Room‐temperature lasing under pulsed excitation with threshold pump intensity at I≊500 kW/cm2 has been achieved, together with high repetition ‘‘quasi‐continuous’’ mode operation at temperatures so far up to 100 K.

Room temperature blue light emitting p-n diodes from Zn(S,Se)-based multiple quantum well structures

Blue (494 nm) light emitting quantum well diodes based on Zn(S,Se) p‐n junctions are demonstrated at room temperature. P‐type Zn(S,Se) is realized by using a nitrogen rf plasma cell. The light emitting diode is formed on homoepitaxial GaAs buffer layers by molecular beam epitaxy. The S fraction of the alloy is selected to provide a lattice match between the II‐VI active region and the GaAs buffer; the result is an active region having a dislocation density below 105/cm−2. The letter discusses emission characteristics as well as the x‐ray rocking curve and transmission electron microscopy characterization of the structures.

Blue/green pn junction electroluminescence from ZnSe‐based multiple quantum‐well structures

The successful p doping of ZnSe by substitutional nitrogen using a plasma cell incorporated into the molecular beam epitaxy chamber has led to the development of electroluminescent devices based on carrier injection at a pn junction. The light emitting diode structures described here are grown on a GaAs substrate using a tetragonally distorted (In,Ga)As buffer layer to provide lattice matching between the substrate and the active II–VI region. The result of the incorporation of the buffer layer is an essentially dislocation‐free active region. The letter discusses optical properties as well as the x‐ray and transmission electron microscopy characterization of the quantum well device structures.

ZnSe based multilayer pn junctions as efficient light emitting diodes for display applications

pn junction characteristics and LED action in ZnSe‐based multilayers grown by molecular beam epitaxy is demonstrated. In particular, we show that (Zn,Cd)Se/ZnSe/Zn(S,Se) structures containing (Zn,Cd)Se quantum wells, grown on p‐type GaAs epilayers, and designed with a heavily doped n+‐ZnSe top contact layer may be appropriate for display device applications in the blue‐green portion of the spectrum.

Low threshold pulsed and continuous‐wave laser action in optically pumped (Zn,Cd)Se/ZnSe multiple quantum well lasers in the blue‐green

Laser action in the blue‐green at room temperature has been achieved in pulsed optically pumped (Zn,Cd)Se/ZnSe multiple quantum well structures at threshold intensities Ith≊30 kW/cm2. Continuous‐wave operation in a II‐VI semiconductor laser has also been demonstrated for the first time, here above 100 K. The role of excitons is found to be of importance in defining the lasing mechanism up to room temperature in these quasi‐two‐dimensional wide‐gap heterostructures.

Indium tin oxide as transparent electrode material for ZnSe‐based blue quantum well light emitters

Sputter deposited indium tin oxide layers have been used as the top contact for blue LEDs and diode lasers in (Zn,Cd)Se/Zn(S,Se) quantum well heterostructures. The contact resistance to n‐Zn(S,Se) is comparable to that with indium or gold. The optically transparent contacts have been utilized, as an example, in the fabrication of a numeric display device and to show that LED emission is of excitonic origin in these type I quantum wells.

Pseudomorphic separate confinement heterostructure blue-green diode lasers

The growth and performance of pseudomorphic separate confinement heterostructure blue‐green laser diodes are described. The devices incorporate the (Zn,Mg)(S,Se) quaternary as cladding layers surrounding a Zn(S,Se) waveguiding layer, and having single or multiple quantum wells of (Zn,Cd)Se. Devices have been operated at room temperature under pulsed conditions (∼1 μs, 10−3 duty cycle) for periods up to 1 h. X‐ray rocking curve full width at half‐maxima as low as 44 arcsec were obtained for a laser structure employing quaternary cladding layers (Mg=9%, S=12%), consistent with transmission electron microscope observations showing no dislocations or stacking faults. The Zn(Se,Te) graded contact was adapted to form an ohmic contact to the top p‐type quaternary layer.