Monolithic integration of a superluminescent diode with a tapered semiconductor power amplifier is proposed, The basic operation of the integrated optical source is demonstrated under pulse conditions, Output power obtained by the integrated device is one to two orders of magnitude higher than the conventional superluminescent diode (SLD) devices.

In order to solve the problem in the conventional superluminescent diode (SLD), i.e. its output power is not high enough for some applications, a monolithic superluminescent source by integrating SLD with the tapered semiconductor amplifier has been designed and fabricated. An AlGaAs heterostructure wafer, gain guide of oxide stripe and a way of direct coupling were adopted. The experimental results show that the superluminescent output of SLD can be amplified for about 22 dB by the tapered optical amplifier. A maximum output power of 580 mW has been obtained under pulsed condition.

Various x-ray techniques have been applied to a study of semiconductor superlattices consisting of 100-period of InxGa1−xAs (15 Å)/GaAs (100 Å) grown on GaAs(100) substrates by molecular beam epitaxy. Structural parameters pertaining to the morphology of interfaces and thickness variations were obtained. The interfaces in these superlattices are found to be highly correlated, and the layers all show a high degree of crystallinity. Splittings in the x-ray reflectivity and diffraction patterns in one of the samples provide clear evidence for pronounced thickness modulation, and direct comparison of the diffraction satellite peaks with results of high resolution transmission electron microscopy indicates that there exists a lateral structural ordering in the [110] direction during epitaxial growth.

We have devised a novel vertical-cavity surface-emitting laser structure. The epitaxial layers have been grown by molecular beam epitaxy (MBE). The bottom mirror consists of 30.5 pairs of multilayer distributed Bragg reflector (DBR). The top mirror is a hybrid reflector consisting of 8.5 pairs of multilayer and a semi-transparent metal film. The structure is obtained by two He ion implantations using tungsten wires as an implant mask. The lowest threshold current is 8.2 mA, and the highest peak light output power is 1.8 mW under room-temperature cw conditions.

Superlattices of 100-period InxGa1−xAs (15 Å)/GaAs(100 Å) grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x-ray scattering techniques. In contrast to the usual superlattice satellite peaks corresponding to structural periodicity along the growth direction, unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample with x=0.535 grown at 480 °C, indicating an in-plane ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the InxGa1−xAs layers gives rise to long-range lateral periodic arrays of clusterlike microstructures with spacing on the order of a few hundred angstroms. This thickness modulation is found to occur only in the [110] direction, thus the material can be viewed as a somewhat disordered array of grown-in parallel quantum wires.

Semiconductor superlattices have been studied by grazing incidence x-ray scattering and x-ray diffraction. For superlattices of 100-period InGaAs/GaAs, lateral structural ordering has been found to occur in the material. For one particular sample (M1400), periodic thickness modulations have been observed in the InGaAs layers. X-ray results also provide evidence for an improvement of interface quality by using interrupt-growth method for 55-period AlAs/GaAs superlattices grown by MBE.

The internal strain in InyGa1−yAs/GaAs and InyAl1−y/GaAs multilayers (y≊0.5) is studied as a function of hydrostatic pressure via Raman scattering. Matching alloy epilayers serve as strain reference samples. Evidence for thermal enhancement of strain‐relaxation under pressure is found in some cases.

Interfacial microstructures in 100-period InxGa1−xAs(15Å)/GaAs(100Å) superlattices grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x-ray scattering techniques. Unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample with x = 0.535 grown at 480°C, indicating an in-plane structural ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the InxGa1−xAs layers gives rise to long-range lateral periodic arrays of cluster-like microstructures with spacing on the order of a few hundred Ångstroms. This thickness modulation is found to occur only in [110] direction, thus the material can be viewed as a somewhat disordered array of grown-in parallel quantum wires.

We have studied by electrolyte electroreflectance and photoluminescence a GaAs/AlGaAs resonant tunneling structure (RTS) with a highly n-doped GaAs cap, before and after hydrogenation. We measured the amount of passivation of shallow donor states and of deep traps in the cap and found the approximate pinning levels and interace charges of the RTS.

Highly doped semiconducting heteroepitaxial structures are commonly found in advanced devices. It is difficult to interpret quantitatively the results of optical measurements on such structures because the strong built-in electric fields present invalidate the low-field theories usually used to interpret those results. We have studied by electrolyte electroreflectance and photoluminescence a GaAs/AlGaAs resonant tunneling structure with a highly n-doped GaAs substrate and cap, before and after hydrogenation. We also have developed a new, improved microscopic theoretical treatment of the effects of strong fields on the local dielectric function and have used that treatment to evaluate quantitatively the effect of hydrogenation on the densities of shallow donor levels and of deep traps in the GaAs cap and to find the interface charges and band-pinning levels in the resonant tunneling junction.

Elastic properties of GaAs/AlAs superlattices have been investigated with use of Brillouin scattering. No evidence of anomalous elastic behavior, such as that reported in many metallic superlattices, is observed. The absence of an anomaly in GaAs/AlAs is consistent with a number of different theories that have been proposed to explain the effects in metallic systems. We also present experimentally determined elastic constants of pure AlAs [${\mathit{C}}_{11}$=(12.1\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}${10}^{11}$ dyn/${\mathrm{cm}}^{2}$ and ${\mathit{C}}_{44}$=(4.74\ifmmode\pm\else\textpm\fi{}0.08)\ifmmode\times\else\texttimes\fi{}${10}^{11}$ dyn/${\mathrm{cm}}^{2}$] and compare them with previous estimates.

Measurements of intersubband transitions and cyclotron resonance (CR) have been carried out on lightly donor-doped GaAs/${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As multiple-quantum-well structures. Absorption coefficients of CR and intersubband resonances combined with calculations of coupling efficiency given an oscillator strength of about 1. Measurements of CR absorption versus pump intensity show clear saturation at high intensities. Results demonstrate that the observed intersubband transitions are due to free electrons and that the large photogenerated excess free-electron density is due to compensation by acceptors.

Results of a far-infrared absorption study of beryllium acceptors in $\frac{\mathrm{GaAs}}{{\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}}$ quantum wells with widths between 300 and 100 \AA{}, as well as a bulk sample of Be-doped GaAs for comparison, clearly show the effects of confinement on the acceptor. The observed increase in transition energy is in qualitative agreement with recent calculations. The intra-acceptor transition data will provide a useful basis for comparison with calculations of higher excited $p$-like states.

The effects of hydrogenation in high-purity p-type GaAs grown by molecular beam epitaxy and metalorganic chemical vapor deposition have been investigated by low-temperature photoluminescence and Hall-effect measurements. Before hydrogenation, photoluminescence measurements showed the dominant acceptor in the original samples was C, while after hydrogenation, the concentration of electrically active C acceptors was significantly reduced and the samples were highly resistive. These electrical and spectroscopic results show that C acceptors in GaAs can be passivated by hydrogenation.

Serum prolactin (PRL) levels in 16 premenopausal subjects on synthetic estrogen and progestin were measured during 19 treatment cycles. The studies were performed during the estrogen segments of the treatment cycle (days 7–16) in 10 subjects receiving sequential contraceptives, and between days 9–20 in 6 subjects receiving combination type contraceptives. Because of the episodic nature of PRL release, the transverse mean of the frequent samples obtained over a period of four hours was used for quantitative comparison of subjects receiving the contraceptive steroids with normal subjects. Significant increases in prolactin concentrations were noted in both sequential (P < 0.001) and combination (P < 0.05) pill users as compared to normals. The mean serum PRL level of subjects on sequential type pill was significantly greater (P < 0.01) than that of subjects on combination type pill. This data suggests that the estrogen component of the pill exerts a positive effect on pituitary prolactin secretion.

The effect of estrogen and progestin on pituitary responsiveness to 150 mug synthetic luteinizing hormone-releasing factor (LRF) was assessed in premenopausal women receiving sequential (n=12) and combination (n=7) contraceptive steroids. A marked contrast in the time-course and maximal response to LRF was found; a prompt but quantitatively smaller luteinizing hormone (LH) response was seen during cyclic combination therapy, while a delayed (five times) but enhanced (fivefold) LH response was observed during estrogen segments of cyclic sequential therapy. For follicle-stimulating hormone (FSH), the maximum rise was also higher, and the peak response was similarly delayed in the latter group. The quantitative secretion in response to LRF for LH (area under the curve), but not for FSH, was significantly greater (P < 0.01) in subjects receiving sequential, as compared to subjects receiving combination treatment. In both groups, characteristic gonadotropin responses to LRF were reproducible and were independent of the duration of treatment. Since LRF studies were performed during the estrogen segment of treatment cycle in subjects receiving sequential steroids, our data suggest that estrogen exerts a direct feedback action at the pituitary level and that pituitary responsiveness to LRF is augmented by estrogen.