Mitsuru Shimazu

Orientation dependence of GaAs growth in low-pressure OMVPE

Abstract The crystallographic orientation dependence of the growth rate and Si doping of GaAs layers grown by low-pressure organometallic vapor phase epitaxy at 10 to 100 Torr has been studied using variously oriented substrates. We found that the growth rate strongly depends on the crystallographic orientation. The growth rate decreases in the order (111)A (001) (110), in proportion to the surface density of Ga atoms in the solid phase at the growth surface. No epitaxial layer was grown on ( 1 1 1 )B substrates under our experimental conditions. These results suggest that the adsorption of arsine to the Ga atoms plays an important role in the surface growth kinetics of GaAs OMVPE. We also found that Si incorporation using disilane as a dopant depends on the crystallographic orientation and the growth temperature.

Selective growth of AlxGa1−xAs embedded in etched grooves on GaAs by low-pressure OMVPE

Abstract Selective growth of Al x Ga 1− x As (0 ⩽ x ⩽ 0.35) embedded in grooves has been achieved by low-pressure OMVPE at 10 Torr. By precise control of the growth thickness, planar buried structures of GaAs and Al x Ga 1− x As multilayers have been obtained in groo 3 to 1000 μm in width. No polycrystalline deposition occurs on areas masked with SiN x films. It has been found that the low-pressure OMVPE growth is remarkably dependent on the crystallographic orientation. In flat-bottomed grooves with vertical side walls, formed by reactive ion beam etching, the layers can be embedded level with the substrate surface, irrespective of whether the groove is in the [110] or [110] direction. In reverse-mesa-shaped grooves formed by chemical etching in the [110] direction, the layers can also be embedded level with the substrate surface. Based on athese results, we discuss growth mechanisms in low-pressure OMVPE, compared to those in atmospheric-pressure OMVPE.

The pyrolysis temperature of triethylgallium in the presence of arsine of trimethylaluminum

Abstract The pyrolysis of triethylgallium (TEG) in H 2 has been investigated using a quadrupole mass spectrometer in a low-pressure (0.1–2.0 kPa) OMVPE growth reactor. The pyrolysis temperature of TEG is influenced by the addition of arsine (AsH 3 ) or trimethylaluminum (TMA). The addition of arsine lowers the TEG pyrolysis temperature and results in the formation of ethane (C 2 H 6 ) and ethylarsines ((C 2 H 5 ) n AsH 3−n , n = 1−3). These poducts indicate the generation of ethyl radicals a nd the reaction between ethyl radicals and arsine. The arsine reacts with the ethyl radical and hence promotes the decomposition of TEG. On the other hand, the addition of TMA to TEG raises the TEG pyrolysis temperature. Only mixing TEG and TMA at room temperature was found to produce methyldiethylgallium (MeEt 2 Ga) and dimethylethylgallium (Me 2 EtGa). These products, which show higher pyrolysis temperatures than pure TEG, can explain the higher TEG pyrolysis temperature for TEG mixed with TMA. These mixed alkyls (Me n Et 3−n Ga, n = 1, 2) are produced most likely through the rapid exchange of alkyl groups due to the equilibrium between dimer and monomer.

Silicon doping using disilane in low-pressure OMVPE of GaAs

Abstract Disilane was studied as a doping gas in low-pressure OMVPE of GaAs. The dependence of Si incorporation on growth temperature was investigated over a wide range of growth pressure from 1 to 100 Torr. At low growth pressures (

Silicon doping from disilane in gas source MBE of GaAs

Disilane (Si2H6) is used as an n-type dopant in gas source molecular beam epitaxial growth of GaAs using triethylgallium (TEG) and AsH3. A linear relationship is obtained between the disilane flow rate and the electron concentration in the range from 1.3×1017 to 1.2×1018 cm-3. The doping efficiency depends on the substrate temperature varied from 480 to 600°C, but only slightly on the AsH3 flow rate. Furthermore, the doping efficiency is observed to be enhanced by a factor of 2.5 when UV laser irradiation is directed normal to the substrate surface.

Long-Wavelength GaInNAs Vertical-Cavity Surface-Emitting Laser With Buried Tunnel Junction

A long-wavelength GaInNAs vertical-cavity surface-emitting laser with a buried tunnel junction (BTJ) has been demonstrated in this paper. It has been shown that a combination of a GaAs-based BTJ for a current confinement, GaInNAs multi-quantum wells for an active region, a dielectric distributed Bragg reflector (DBR) for a top mirror, and an AlGaAs/GaAs DBR for a bottom mirror is desirable to realize high-speed operation at high temperature. The maximum output power of 4.2 mW with a low resistance of 65 Omega has been obtained at 25degC. Operations of 10 Gb/s have been achieved over the temperature range of 25degC-85degC, with operation current of 6.9 mA and extinction ratio of 5.0 dB.

High power and low resistive GaInNAs-VCSELs with buried tunnel junctions

GaInNAs-VCSELs with buried tunnel junction structures are proposed and demonstrated. The maximum output powers of 4.2 mW at 25degC and 2.2 mW at 85degC are achieved with a low resistance of 65 Omega.

100°C, 10 Gbps operation of buried tunnel junction GaInNAs VCSELs

10 Gbps operation of BTJ GaInNAs VCSELs is achieved over temperature range of 25degC to 100degC with operation current of 5.6 mA and extinction ratio of 4.2 dB.

A novel method for gas temperature measurements in low-pressure OMVPE reactors

Abstract Organometallic vapor phase epitaxy (OMVPE) is one of the most important epitaxial growth techniques. We have developed a novel method of determining gas temperatures in a low-pressure OMVPE reactor in the basis of the kinetic theory of gases. The method was applied to study the temperature profiles in the reactor using a movable fine capillary for gas sampling, for different flow velocities (3.6 and 7.2 cm/s), pressures (0.1 and 1.0 kPa) and susceptor temperatures (400 and 600°C). The results show that the temperature profiles at low pressures are less steep, compared to those at atmospheric pressure. Changes in the pressure and flow velocity result in only small variations in the profiles. No convection effects were observed in the profiles. This new method offers the advantages of simplicity and accuracy.

Ultraviolet light irradiation effects on silicon doping into GaAs using disilane in OMVPE

Abstract In low-pressure (1.3 kPa) n-GaAs OMVPE, irradiation of 240–300 nm ultraviolet (UV) light has been found to enhance silicon doping with disilane (Si 2 H 6 ), even though the wavelengths of the UV light are longer than the absorption edge (200 nm) of Si 2 H 6 . Trimethylgallium (TMG) and arsine (AsH 3 ) were used as starting materials. The [AsH 3 ]/[TMG] and [Si 2 H 6 ]/[TMG] ratios were 80 and (2.5-5.0)X10 -4 , respectively. The increase rate ( Δ n / n ) of the electron concentration ( n ), due to the UV light irradiation, was examined as a function of the growth temperature. The maximum Δ n/ n was obtained at 600°C, and no enhancement could be observed below 500°C. The observed temperature dependence of the doping enhancement corresponded well to the concentrations of the reaction products SiH 3 AsH 2 and (CH 3 ) n SiH 4 - n ( n =1−3). A doping enhancement mechanism, which includes photodecomposition of metastable intermediate products generated by reactions between source gases on the growth surface, is presented.