Akbar Nouhi

Heteroepitaxial growth of Cd1−xMnxTe on GaAs by metalorganic chemical vapor deposition

In this letter we report on preliminary results of heteroepitaxial growth of the dilute magnetic semiconductor alloy Cd1−xMnxTe on GaAs by metalorganic chemical vapor deposition. Dimethylcadmium (DMCd), diethyltellurium (DETe), and tricarbonyl (methylcyclopentadienyl) manganese (TCPMn) were used as source materials. The TCPMn had to be heated to as high as 140 °C to provide the required vapor pressure. Films with Mn atomic fractions up to 30% have been grown over the temperature range 410–450 °C. Results of optical absorption/transmission, photoluminescence, and x‐ray diffraction measurements are presented along with a scanning electron micrograph showing good surface morphology of the grown layers.

Facet modulation selective epitaxy–a technique for quantum-well wire doublet fabrication

The technique of facet modulation selective epitaxy and its application to quantum-well wire doublet fabrication are described. Successful fabrication of wire doublets in the AlxGa1–xAs material system is achieved. The smallest wire fabricated has a crescent cross section less than 140 A thick and less than 1400 A wide. Backscattered electron images, transmission electron micrographs, cathodoluminescence spectra, and spectrally resolved cathodoluminescence images of the wire doublets are presented.

Molecular beam epitaxy and metalorganic chemical vapor deposition growth of epitaxial CdTe on (100) GaAs/Si and (111) GaAs/Si substrates

Epitaxial CdTe has been grown on both (100)GaAs/Si and (111)GaAs/Si substrates. A combination of molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) has been employed for the first time to achieve this growth: the GaAs layers are grown on Si substrates by MBE and the CdTe film is subsequently deposited on GaAs/Si by MOCVD. The grown layers have been characterized by x‐ray diffraction, scanning electron microscopy, and photoluminescence.

High-peak-power low-threshold AlGaAs/GaAs stripe laser diodes on Si substrates grown by migration-enhanced molecular beam epitaxy

A high‐peak‐power low‐threshold AlGaAs/GaAs double‐heterostructure stripe laser diode on Si substrates grown by hybrid migration‐enhanced molecular beam epitaxy (MEMBE) and metalorganic chemical vapor deposition (MOCVD) has been demonstrated for the first time. These devices showed the highest peak powers of up to 184 mW per facet reported so far for double‐heterostructure stripe laser diodes on Si substrates, room‐temperature pulsed threshold currents as low as 150 mA, and differential quantum efficiencies as high as 30% without mirror facet coating. An intrinsic threshold current density has been estimated to be about 2 kA/cm2 when taking current spreading and lateral diffusion effects into account. Low dislocation density shows that MEMBE can be a useful method to grow high quality GaAs and AlGaAs/GaAs layers on Si substrates by combining with MOCVD.

Low‐temperature deposition of low resistivity ZnSe films by reactive sputtering

Low resistivity semiconducting films of ZnSe have been deposited at temperatures as low as 120 °C using dc magnetron co‐sputtering of Zn and In (dopant) targets in a reactive atmosphere of H2Se/Ar. Yellowish transparent films of ZnSe on glass and conductive transparent oxide‐coated glass substrates were obtained having a room‐temperature resistivity as low as 20 Ω cm. Atomic absorption analysis showed a Zn to Se ratio of 49.8:49.0 and In concentration of about 1% for the reactively sputter‐deposited ZnSe:In films on glass. Optical absorption/transmission measurements yielded an energy band gap of about 2.65 eV at room temperature. X‐ray diffraction results indicated highly oriented polycrystalline films on glass with the c axis parallel to the plane of the film.

High Peak Power Low Threshold AlGaAs/GaAs Stripe Laser Diodes On Si Substrates By Hybrid MBE/MOCVD Growth

We report high peak power low threshold AlGaAs/GaAs double heterostructure stripe geometry laser diodes on Si substrates grown for the first time by hybrid migration-enhanced MBE (MEMBE) and MOCVD. The lasers with 6 pm silicon oxide stripes were tested unmounted under pulsed conditions (i.e., 50 ns pulse width and 10 KHz pulse repetition rate) at room temperature. These lasers show a peak output power as high as 184 mW per facet and a threshold current as low as 150 mA at 300 K for a cavity length of 350 μm. The differential quantum efficiency of 30 % was obtained without mirror facet coating. A threshold current density of 7 kA/cm2 was obtained based on the nominal stripe dimensions without considering current spreading and lateral diffusion; we estimate about 2 kA/cm2 when taking these effects into account. For comparison, the pulsed threshold current density of the broad area DH lasers on GaAs substrates was 1.1 kA/cm2 at room temperature. This would be further reduced for lasers with a quantum well (e.g., GRIN-SCH SQW) active region. These results show the highest output peak power reported so far with a low threshold current for conventional double heterostructure stripe laser diodes grown on Si substrates.

Growth And Characterization Of CdTe On GaAs/Si Substrates

Epitaxial CdTe has been grown on both (100) GaAs/Si and (111) GaAs/Si substrates. A combination of molecular beam epitaxy and metal organic chemical vapor deposition have been employed to achieve this growth. The GaAs layers are grown on Si substrates by molecular beam epitaxy, followed by the growth of CdTe on GaAs/Si substra by metalorganic chemical vapor deposition. X-ray diffraction, photoluminescence and scanning electron microscopy have been used to characterize the CdTe films.

Heteroepitaxy of CdTe on GaAs-ON-Si

CdTe is a semiconductor with numerous applications, the most prominent of which is its use as a buffer layer for the growth of epitaxial films of HdCdTe for infrared detector arrays. However, bulk CdTe is extremely difficult to grow and the non-availability of high quality, large area, inexpensive, single crystal CdTe has slowed the development of HgCdTe detectors. Infrared (IR) device processing requires large areas of single crystal material, and the problems associated with bulk CdTe are now being circumvented by utilizing alternative substrates on which CdTe can first be grown epitaxially. This in turn serves as a buffer layer for the growth of HgCdTe.