A layer structure, grown in a single step, and a fabrication process were developed for the monolithic integration of AlGaAs/GaAs optoelectronic smart pixels. Metal semiconductor field-effect transistors (MESFETs), light-emitting diodes (LEDs) and photodiodes (PDs) were designed in such a way that the light emitted from the LEDs can efficiently be detected by the PDs. An example is presented of a fabricated optoelectronic smart pixel: a threshold circuit consisting of a dual-photodiode differential input, an inverter and a current-balanced output containing an LED. The circuit shows a switching energy of 2 pJ. The minimum switching power is <1 nW with a contrast ratio >1000. The maximum light output of the LED is 18 mu W With an overall power dissipation of 20 mW.

We present results on visible red top-emission microcavity light-emitting diodes grown by metal organic chemical vapor deposition. The emission characteristics dependence with respect to the detuning between the quantum well emission and the cavity mode was experimentally investigated. The detuning was varied during growth by 60 nm across a 2 in. wafer radius according to a parabolic and reproducible dependence with respect to the position on the wafer. Numerical simulation reproduced very well the experimental results using the internal quantum efficiency ηint as a fitting parameter, resulting in a value of ηint=56%+/−5% at a current density of 20 A/cm2.

We have investigated the electroabsorption due to the Franz–Keldysh effect in GaInP/AlGaInP p-i-n double heterostructures grown by metalorganic vapor phase epitaxy. The simultaneous evaluation of transmission and photocurrent measurements allowed an accurate determination of the field dependent absorption coefficient of ordered and disordered GaInP alloys. For ordered and disordered material, similar changes of the absorption coefficient as high as 4000 cm−1 have been observed for field changes of ΔE=250 kV/cm. Thermally disordered samples, however, showed a degradation of the electrical and optical properties.

Top-emitting AlasAlGaAs vertical cavity surface emitting lasers emitting at 765 nm with minimum threshold currents of 0.6 mA and threshold voltages of 1.9 V have been grown by MOVPE. In order to keep the growth time low, we investigated the possibility to grow these structures at growth rates of 5 μm/h. Special attention was paid to the homogeneity that can be achieved over a 2″ wafer under these growth conditions. Spatially resolved reflectivity measurements on GaAsAlAs distributed Bragg reflectors showed, that the growth rate varies less than 0.3% in the center of the wafer and decreases by 1% at the wafer edge.

Under certain growth conditions GalnP tends to exhibit spontaneous superlattice ordering with atoms arranging in GaP/lnP monolayers along two of the possible four [111] crystal directions. The superlattice ordering leads to significant changes in the electrical and optical properties of the crystal most prominently decreasing the energy band gap. In ordered material optical transitions between the highest valence band and the conduction band are not allowed for polarisation parallel to the ordering directions. In order to demonstrate the potential device applications of this polarisation effect we have studied the electroluminescence (EL) and the electroabsorption of (Al0.3Ga0.7)0.52In0 48/Ga0 52ln0.48P p-i-n double hetero structures. Samples with ordered (o-samples) and disordered (d-samples) GalnP active layers have been grown lattice matched to GaAs by metal organic vapour phase epitaxy (MOVPE). The o-samples were grown at 650°C on exactly oriented GaAs substrates while for the d-samples a growth temperature of 710°C and 6° toward [111A] tilted substrates have been used. Moreover, thermal disordering of the o- samples was achieved by rapid thermal annealing (RTA) at 900°C for 30 sec after growth (a-samples). This technique allows to compare ordered and disordered material made from the same epitaxial wafer. Surface emitting light emitting diodes (LED) with chemically dry etched mesas have been fabricated. The EL spectra of o- and a-LED show peaks at 673 nm and 650 nm respectively. This corresponds to an energy shift of 65 meV and is in very good agreement with PL measurements. The a-samples exhibit a significantly decreased EL-efficiency compared to the o-LED which can be explained by damage caused by RTA. Polarisation measurements of o-LEDs exhibit a contrast of 1.4 dB between polarisation parallel to the [ 01 1 ¯ ] and [011] crystal direction respectively. This effect is nearly independent of diode current and mesa geometry, but not observed for a-LEDs. This lifted degeneracy of polarisation states associated with the ordered GalnP phase has to be considered as a very promising feature for polarisation control in VCSELs.

We report on polarization effects in surface emitting light emitting diodes based on p-i-n AlGaInP/GaInP double heterostructures grown by metal organic vapor phase epitaxy. Devices with an ordered GaInP active layer show polarized light output with a ratio of 4:3 for polarization along the [011] and [011̄] crystal direction, respectively. This polarization is nearly independent of diode current and mesa geometry, but is not observed if disordered GaInP active layers are used. The effect is considered to be an important means for polarization control in vertical cavity surface emitting lasers.

We have fabricated AlAs/AlGaAs Vertical Cavity Surface Emitting Lasers (VCSELs) emitting at 765 nm with record performance. The VCSELs were fabricated using MOVPE and a combination of dry and wet etching for the lateral structuring of the laser posts. Minimum threshold currents of 600 μA and threshold voltages of 1.9 V are achieved for VCSELs with a mesa diameter of 26 μm. The maximum slope efficiencies are 0.46 W/A with wallplug efficiencies of 11.2 % at an output power of 1 mW. The maximum output powers for larger devices exceed 5 mW. To our knowledge these are the best performance characterstics for VCSELs operating in the 760 - 780 nm wavelength range. Compared to recently published data on 780 nm VCSELs in the GalnAsP/AlGalnP material system, the threshold currents ate more than a factor of 4 smaller, the wallpug efficiencies are a factor of 1.7 larger. We attribute the high performance to the accurate control over growth rates and aluminum contents, the layer design and the improved lateral current confinement by an additional lateral selective etching step. Spectral measurements show that the lasers operate single transverse mode over a wide current range with single mode output powers above 1 mW. A comparison with conventional mesa-etched VCSEL structures is made to demonstrate the impact of the additional lateral etching step on the device performance.

Near infrared (765 nm) AlAs/AlGaAs vertical-cavity surface emitting laser (VCSEL) diodes with minimum threshold currents of 0.6 mA and threshold voltages of 1.9 V are demonstrated. The peak output powers exceed 5 mW. These characteristics represent a significant improvement compared to previously published data for VCSELs operating in this wavelength range.

The surface topography during initial and steady state epitaxial growth of InP on InP is monitored with in situ diffuse elastic light scattering. The in situ results are compared with the end-of-run topography measured by ex situ atomic force microscopy. Upon growth initiation, an increase in surface roughness is observed with steps oriented perpendicular to the [011] and [010] direction. After several nanometers of InP deposition, the surface topography planarizes and steady state step-flow epitaxy develops with steps aligned to the pregrowth terrace.

An AlGaAs/GaAs layer structure, grown in a single step, and a fabrication process has been developed for the monolithic integration of cascadable optoelectronic smart pixels. Metal semiconductor field-effect transistors (MESFETs), light-emitting diodes (LEDs) and photodiodes (PDs) are used for the integration. As an example a threshold circuit consisting of a dual-photodiode input and a current balanced output containing an LED is presented. The circuit shows a switching energy of 2 pJ and a minimum switching power of 3 nW. The maximum light output of the LED is 30 mW with a contrast ratio > 1000. The overall power dissipation is 15 mW.

Native oxide technology is used to fabricate long wavelength (lambda approximately 1.3 mum) InAlAs-InP-InGaAsP quantum well heterostructure laser diodes with a buried oxide undercutting and constricting the ridge-waveguide active region. The buried native oxide of InAlAs constricts the current and reduces edge and surface losses. Data are presented showing threshold currents as low as approximately 140 mA for approximately 13-mum-wide stripes (L approximately 750 mum), with maximum continuous wave output powers as high as approximately 225 mW/facet and external differential quantum efficiencies up to 67% (300 K, uncoated facets).

Native oxide technology is used to fabricate long wavelength (λ∼1.3 μm) InAlAs-InP-InGaAsP quantum well heterostructure laser diodes with a buried oxide undercutting and constricting the ridge-waveguide active region. The buried native oxide of InAlAs constricts the current and reduces edge and surface losses. Data are presented showing threshold currents as low as ∼140 mA for ∼13-μm-wide stripes (L∼750 μm), with maximum continuous wave output powers as high as ∼225 mW/facet and external differential quantum efficiencies up to 67% (300 K, uncoated facets).

The topographical evolution of the (100) GaAs surface annealed under an arsine/hydrogen ambient is studied by in situ orientation-resolved light scattering and ex situ atomic force microscopy (AFM). The light scattering system provides real-time monitoring of the magnitude and crystal orientation of topographical features of 0.3 μm scale. The AFM images of the GaAs surface, quenched at various annealing temperatures, vividly depict the randomly oriented high density monolayer steps evolving into an atomically smooth terracelike structure.

In situ elastic light scattering was used to characterize, in real-time, the topography of InP-InGaAsP and GaAs epitaxial layers grown by metalorganic chemical vapor deposition (MOCVD). Phenomena such as the evolution of the atomic terrace and interface included roughness were observed. Ex situ atomic force microscopy images provide corroboration of the in situ data

The evolution of surface topography during epitaxial growth of GaAs on (100) GaAs substrate is observed using angle-resolved elastic light scattering within a metalorganic chemical vapor deposition reactor. The temporal and orientation dependence of diffuse (nonspecular) optical scattering is determined at growth initiation, during steady state growth, and at growth conclusion. Phenomena such as persistent monolayer oscillations in surface roughness, nucleation delay, and [01̄1] step development are observed. The influence of substrate miscut, growth temperature, and rate is discussed.