We report the study of lasing modes in broad-area, equilateral-triangular laser cavities. An alternative approach is proposed to study optical modes in equilateral triangular cavities in an analytical form. The modes were obtained by examining the simplest optical paths inside the cavity, which yields the final solution with the boundary conditions. The cavities can be fabricated from semiconductor heterostructures grown on (111)-oriented substrates, which can be easily cleaved into equilateral triangular shapes. Such a design takes advantage of total internal reflection at the cleaved facets of the cavity for circulating modes. Experimental results obtained from cavities fabricated from a superlattice structure of In0.13Ga0.87As/GaAs grown on a (111) GaAs substrate.

We report on a magnetophotoluminescence study of an n-type modulation doped Al0.3Ga0.7As (Si)/AlAs/GaAs/AlAs/Al0.3Ga0.7As (Si) quantum-well structure in which a dense electron gas populates the AlAs X valleys. The interband transitions in this system are type II and exhibit GaAs and AlAs LO-phonon replicas. In the presence of a magnetic field applied perpendicular to the structure's layers luminescence features associated with the l=0 and l=1 Landau levels of the AlAs X-z valleys were resolved. The slope dE/dB of these transitions yield an in-plane effective mass m* of 0.44. [S0163-1829(99)10411-9].

The effect of spacers in modulation-doped Zn1−xCdxSe/ZnSe:Cl multiple quantum wells (MD-MQWs) was investigated by photoluminescence (PL) and time-of-flight secondary-ion-mass spectrometry (TOF-SIMS). A comparison was made between structures with and without spacers as a function of annealing temperature. The diffusion of Cl and Cd was monitored by TOF-SIMS depth profiling and photoluminescence. Although TOF-SIMS does not show any significant diffusion of Cl and Cd in both structures at temperatures up to 385 °C, the PL results indicate the modification of optical properties in the Zn1−xCdxSe/ZnSe:Cl MD-MQWs due to annealing. Up to an annealing temperature of 385 °C, the MD-MQWs with spacers show superior optical quality in the quantum well regions, while quenching of the quantum well band-edge PL and strong enhancement of deep-level emission were observed from the MD-MQWs without spacers. This phenomenon suggests that the radiative deep-level emission may provide more efficient channel for electron–hole recombination with increasing annealing temperature.

p-i-n photodiodes were fabricated on nitrogen ion implanted undoped ZnSe/n-type ZnSe epilayers grown on n+GaAs (100) substrates by molecular beam epitaxy. To obtain a quasi-uniform p layer doping profile, nitrogen ions at multiple energies and ion doses were implanted at room temperature. The activation of implanted species was carried out by an optimized post-annealing in a nitrogen ambient. Optical studies were performed on the implanted/annealed devices by photoluminescence spectroscopy at 10 K, which indicated donor–acceptor pairs at an energy of 2.7 eV and its phonon replicas with 30 meV intervals. The circular p-i-n diodes with a 1 mm diam contact area showed a device breakdown voltage to be linearly dependent on the thickness of the undoped ZnSe epilayer. For p-i-n diodes fabricated on an initial 0.5 μm thick undoped ZnSe layer, an ideality factor of 1.19 and a reverse bias breakdown voltage of 12 V was observed. A large photocurrent, good linearity with light intensity, and low dark current were observed. A photocurrent/dark current ratio >105 was obtained at an illumination intensity of 100 mW/cm2. These devices exhibited a responsivity of 0.025 A/W at a wavelength of 460 nm through the top 200 Å thick metal contacts.

We have studied the luminescence intensity associated with type-I and type-II interband transitions in several CdSe/ZnTe quantum well structures as a function of CdSe layer thickness. It was found that as the CdSe layers become wider, the intensity of the type-I transition increases, while that of the type-II transition decreases. These results are analyzed in terms of a variational calculation which takes into account the Coulomb interaction between the electrons and holes that participate in the interband transitions.

The photoluminescence spectra of n-type modulation doped GaAs/AlAs quantum wells with well width of 80 Angstrom exhibit a pronounced enhancement of the photoluminescence intensity associated with electrons at the Fermi energy. This enhancement is not observed in wider wells. The effect disappears when the temperature is raised above 70 K. The observed enhancement of the photoluminescence is attributed to the proximity of the Fermi energy to the donors in the AlAs barriers. When the l=1 Landau levels are tuned above the donor states, there is strong indication that electrons are transferred from the GaAs wells to the AlAs barriers.

Nitrogen ions were implanted into ZnSxSe1−x epilayers grown on p-GaAs (100) substrates by molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD). Dopant activation and annealing out the implant damage were achieved by a postannealing process in a N2 ambient. Schottky structures employing the implanted p-type ZnSxSe1−x were fabricated and device efficacy was examined by photoluminescence (PL) spectroscopy, current–voltage (I–V), current–voltage temperature (I–V–T), and high frequency capacitance–voltage (C–V) measurements. PL spectra showed a clear donor–acceptor pair (DAP) recombination at an energy of 2.735 and 2.72 eV, in both MBE and MOCVD ZnSSe epilayers, respectively, regardless of the postannealing temperatures. The diode conduction in forward bias proceeds by the combination of thermionic and tunneling emission. C–V measurement proved the maximum doping concentration to be around 1017 cm−3 after ion implantation.

We have studied the band-edge photoluminescence from two n-type modulation-doped ZnSe/ZnxCd1-xSe single quantum-well structures with electron areal densities of 1.1 x 10(12) and 1.9 x 10(12) cm(-2) in magnetic fields up to 30 T. The sharp excitonic transitions observed in undoped samples are replaced by a broad luminescence band. In a magnetic field, the luminescence spectra consist of distinct features associated with interband transitions between electrons occupying the conduction-band Landau levels and photoexcited holes. The energies of these transitions exhibit anomalies for even filling factors due to many-body effects.

We report measurements of electron transfer in real space in GaAs/AlxGa1−xAs asymmetric double quantum wells under an electric field by far-infrared cyclotron resonance (CR). Due to nonparabolicity, the asymmetric quantum structure results in well-resolved CR lines, which allow contactless measurements of the electron density in each well. Our results show that electrons tunnel through the barrier from one well to the other at the level anticrossing of their ground states.