Trisdimethylaminoarsenic Research Articles

MOCVD Grown HgCdTe Heterostructures for Medium Wave Infrared Detectors

This paper presents the current status of medium-wave infrared (MWIR) detectors at the Military University of Technology’s Institute of Applied Physics and VIGO System S.A. The metal–organic chemical vapor deposition (MOCVD) technique is a very convenient tool for the deposition of HgCdTe epilayers, with a wide range of compositions, used for uncooled infrared detectors. Good compositional and thickness uniformity was achieved on epilayers grown on 2-in-diameter, low-cost (100) GaAs wafers. Most growth was performed on substrates, which were misoriented from (100) by between 2° and 4° in order to minimize growth defects. The large lattice mismatch between GaAs and HgCdTe required the usage of a CdTe buffer layer. The CdTe (111) B buffer layer growth was enforced by suitable nucleation procedure, based on (100) GaAs substrate annealing in a Te-rich atmosphere prior to the buffer deposition. Secondary-ion mass spectrometry (SIMS) showed that ethyl iodide (EI) and tris(dimethylamino)arsenic (TDMAAs) were stable donor and acceptor dopants, respectively. Fully doped (111) HgCdTe heterostructures were grown in order to investigate the devices’ performance in the 3–5 µm infrared band. The uniqueness of the presented technology manifests in a lack of the necessity of time-consuming and troublesome ex situ annealing.

Growth mechanism of GaAs1-xSbx ternary alloy thin film on MOCVD reactor using TMGa, TDMAAs and TDMASb

Metal Organic Chemical Vapor Deposition (MOCVD) is a method for growing a solid material (in the form of thin films, especially for semiconductor materials) using vapor phase metal organic sources. Studies on the growth mechanism of GaAs1-xSbx ternary alloy thin solid film in the range of miscibility-gap using metal organic sources trimethylgallium (TMGa), trisdimethylaminoarsenic (TDMAAs), and trisdimethylaminoantimony (TDMASb) on MOCVD reactor has been done to understand the physical and chemical processes involved. Knowledge of the processes that occur during alloy formation is very important to determine the couple of growth condition and growth parameters are appropriate for yield high quality GaAs1-xSbx alloy. The mechanism has been studied include decomposition of metal organic sources and chemical reactions that may occur, the incorporation of the alloy elements forming and the contaminants element that are formed in the gown thin film. In this paper presented the results of experimental data on the growth of GaAs1-xSbx alloy using Vertical-MOCVD reactor to demonstrate its potential in growing GaAs1-xSbx alloy in the range of its miscibility gap.

Effects of source gas molecules on N–H- and N–D-related defect formations in GaAsN grown by chemical beam epitaxy

The formation mechanism of N–H-related defects in GaAsN grown by chemical beam epitaxy (CBE) is studied on the basis of the isotope effects on the local vibration modes (LVMs) originating from N–H. When deuterated monomethylhydrazine (MMHy) is used as the N source, LVM signals from the nitrogen–deuterium bond (N–D) are obtained. However, there are still N–H peaks in the IR absorption spectra, which have intensities similar to those of N–D peaks. When the film is grown with deuterated triethylgallium (TEGa), there are no N–D peaks. The peak intensity at 2952 cm−1 increases with increasing tris(dimethylamino)arsenic (TDMAAs) flow rate, and that at 3098 cm−1 is almost constant regardless of the flow rate. These results indicate that H atoms in the N–H-related defects originate from H directly bonded to N in MMHy and CH3 in MMHy and/or H in TDMAAs, not from TEGa.

Improved luminescence efficiency of InAs quantum dots grown on atomic terraced GaAs surface prepared with in‐situ chemical etching

AbstractObservation of the enhanced luminescence efficiency of InAs quantum dots (QDs) grown on atomically controlled GaAs surfaces is reported. With the trisdimethylaminoarsenic (TDMAAs) in‐situ surface etching process, formation of atomic steps and terraces on GaAs surfaces were clearly observed. InAs QDs grown on the processed GaAs surfaces showed the clear dependence of QDs size, density and optical characteristics on the surface properties, i.e., the increase of the QDs height and diameter the decrease of the QDs density. About 6‐times enhancement of photoluminescence efficiency which has the peak around 1550‐nm wavelength was observed by growing InAs QDs on atomically controlled GaAs surfaces. This is due to the migration enhancement of InAs during thegrowth the QDs. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Metal-Organic Chemical Vapor Deposition of Hg1−x Cd x Te Fully Doped Heterostructures Without Postgrowth Anneal for Uncooled MWIR and LWIR Detectors

Uncertainty in precursor pulse delays and shapes has been found to be an important factor in Hg1−x Cd x Te metal-organic chemical vapor deposition (MOCVD) growth using the interdiffused multilayer process (IMP). Herein, metal-organic concentration changes in the growth zone are examined using an in␣situ infrared (IR) absorption gas monitoring system, and modifications to the interdiffused multilayer process are applied for in␣situ control of stoichiometry, improved morphology, minimized process length, and consumption of precursors. Dimethylcadmium (DMCd) introduction during IMP flush stages in HgTe was used for stoichiometry control. The final stage of heterostructure formation was optimized to prevent Hg outdiffusion. As a result, vacancy concentration was reduced far below the equilibrium level at the growth conditions so the background of n-type doping was revealed. Acceptor doping with arsine (AsH3) and trisdimethylaminoarsenic (TDMAAs) was examined over a wide range of compositions, and doping levels of 5 × 1015 cm−3 to 5 × 1017 cm−3 were obtained. The presence of both arsenic dopants significantly increased the CdTe growth rate. This caused an increase of Cd mole fraction in the grown material. Doped heterostructures can be grown without any postgrowth anneal and used for mid- and long-wavelength infrared (MWIR and LWIR) devices operating at near-ambient temperatures.

Chemical beam epitaxy of InGaAsN films for multi-junction tandem solar cells

Chemical beam epitaxy (CBE) offers a new growth technique for InGaAsN films that are expected to provide the third cell in an ultra-efficiency 4-junction tandem III–V solar cell. In the CBE system, the selection of arsenic (As) and nitrogen (N) sources is important, so the decomposition processes of As (TBAs, TDMAAs) and N (DMHy, MMHy) precursors were investigated with substrate temperature. Both tertiarybutylarsine (TBAs) and trisdimethylaminoarsenic (TDMAAs) were decomposed at a low temperature (<300 °C). While methyl alkyl and tertiarybutyl radical were produced by decomposition of TBAs, Dimethylamine and Aziridine were produced during the decomposition of TDMAAs. The residual carbon concentration in GaAs films grown with TDMAAs was less than 10 16 cm −3. The incorporation of N in GaAsN films grown with DMHy and MMHy decreased with increasing substrate temperature, and the incorporation of N in GaAsN films grown with MMHy was higher.

Decomposition of trisdimethylaminoarsenic and As nucleation on GaAs(001)-2×4 at low temperature

Adsorption and decomposition of trisdimethylaminoarsenic (TDMAAs) on a GaAs(001)-2×4 surface have been studied in the temperature range from 100 to 500 K by high-resolution electron energy loss spectroscopy (HREELS) and scanning tunneling microscopy (STM). TDMAAs is adsorbed molecularly on the surface at 100 K. Decomposition starts at about 300 K and vibration peaks of HREELS spectra due to adsorbates almost disappear between 400 and 500 K. STM images indicate that TDMAAs is adsorbed on As dimers of the GaAs(001)-2×4 surface. Only As atoms and clusters remain at the edge of the As dimer rows and nucleation of As starts at about 470 K. Decomposition of TDMAAs and As nucleation at relatively low temperature are advantageous as a source molecule in metalorganic chemical vapor deposition for nanofabrication.

Magnetic and optical properties of Mn-including InAs dots grown by metalorganic molecular beam epitaxy

Mn-including InAs dot structures are grown on GaAs substrates by metalorganic molecular beam epitaxy (MOMBE), where Mn atoms are first deposited and then TMIn (trimethylindium) and TDMAAs (trisdimethylaminoarsenic) are supplied on GaAs substrate. Mn-including InAs dots as well as Stranski–Krastanov (S–K) mode-grown small-size InAs dots are formed on the surface. Magnetization measurement using a SQUID (superconducting quantum interference device) indicates that the easy axis of magnetization for the Mn-including InAs dots is perpendicular to the GaAs surface. The temperature dependence of magnetization suggests that Mn atoms nuclei may consist of MnGa or MnGa-rich MnGaAs. The formation process of Mn-including InAs dots is studied and the growth condition that only Mn-including InAs dots (disk-like dots) are formed is obtained. Photoluminescence (PL) emission from Mn-including InAs dots is observed.

Scanning tunneling microscopy study of organometallic molecules adsorbed on a GaAs(001)-2×4 surface

The interaction of tertiarybutylarsine (TBAs), triisobutylgallium (TiBGa) and trisdimethylaminoarsenic (TDMAAs) with the GaAs(001)-2×4 surface is studied by scanning tunneling microscope. No adsorbates were observed after TBAs exposure at room temperature. In the case of TiBGa and TDMAAs, adsorbates were observed on the As dimer rows. They were adsorbed randomly at low coverage and formed a 4×4 structure at a full monolayer. Weak interaction between molecules and the GaAs surface is expected because the 2×4 structure of the clean surface was kept under the adsorbates.

InAs dots including Mn atoms fabricated by MOMBE

InAs quantum-dot structures including Mn atoms are fabricated on GaAs substrate by metalorganic molecular beam epitaxy (MOMBE) method. Mn atoms are first deposited on GaAs substrate and InAs dots are formed at the Mn atoms nuclei (probably in the form of MnAs) using TMIn (trimethylindium) and TDMAAs (trisdimethylaminoarsenic) sources. Large-size InAs dots including Mn atoms as well as Stranski–Krastanov (S–K) mode-grown small-size InAs dots are formed on the surface. The small-size InAs dots are subsequently removed by in situ etching with bisdimethylaminoarsenicchloride (BDMAAsCl), and only InAs dots including Mn atoms are left. Growth temperature dependence of the formed InAs dots supports this process. These are confirmed by atomic force microscopy (AFM) and magnetic force microscopy (MFM) measurements. The magnetization properties are measured with a superconducting quantum interference device (SQUID) magnetometor and it is found that the easy axis of magnetization for InAs dots including Mn atoms is perpendicular to the GaAs surface.

Formation of InAs quantum dots by metalorganic molecular beam epitaxy using trisdimethylaminoarsenic and bisdimethylaminoarsenicchloride

InAs quantum dot structures having no wetting layer are fabricated on GaAs substrates by MOMBE (metalorganic molecular beam epitaxy). InAs dot structures with wetting layers are first formed by Stranski–Krastanov growth mode with TMIn (trimethylindium) and TDMAAs (trisdimethylaminoarsenic). The InAs wetting layers are subsequently removed by in situ etching with BDMAAsCl (bisdimethylaminoarsenicchloride). The etching rate of InAs increases exponentially with temperature and linearly with BDMAAsCl flow rate, and is much higher than that of GaAs, which makes it possible to selectively etch the InAs wetting layers. InAs quantum dot structures having Mn atoms inside are also fabricated by the predeposition of Mn atoms acting as nuclei for the enhanced decomposition of TMIn molecules.

Surface reaction of trisdimethylaminoarsenic on GaAs(001)-c(4×4) and (4×6)

The surface decomposition of trisdimethylaminoarsenic (TDMAAs) on GaAs (001) has been studied employing supersonic molecular beam scattering. It was found that TDMAAs molecules adsorbed dissociatively on GaAs (001) surfaces at room temperature through a Langmuir adsorption mechanism. The initial Ga-rich (4×6) surface changed into an As-rich c(4×4) surface after the injection of TDMAAs. The species such as dimethylamine and methylmethyleneimine desorbed at the surface temperatures of 150 and 230 °C, respectively, as measured by temperature-programmed desorption (TPD) spectra. The polar-angle dependence of desorption showed that the desorption of species has two maximal intensities, at the directions along surface normal and 60°, respectively.

MOMBE growth of InGaAs using trisdimethylaminoarsenic

Abstract InGaAs layers were grown by metalorganic molecular beam epitaxy (MOMBE) using trimethylindium (TMIn), triethylgallium (TEGa) and unprecracked trisdimethylaminoarsenic (TDMAAs). Substrate temperature dependence of the growth rate and In composition of InGaAs for the fixed TMIn, TEGa and TDMAAs flow rates are similar to those for the use of TMIn, TEGa and thermally cracked arsine (AsH3). Mirror-like surface In0.53Ga0.47As layers lattice matched to InP are successfully grown, for the first time, using TDMAAs as an As precursor. Growth rate is 0.3 μm/h and electron concentration is 3 × 1016cm−3. 77 K photoluminescence spectrum has a band-to-band transition peak with a full width at half-maximum as narrow as 9.8 meV.

Self-Organized CdSe Quantum Dots on (100)ZnSe/GaAs Surfaces Grown by Metalorganic Molecular Beam Epitaxy

II–VI semiconductor low-dimensional structures, quantum dots, have been grown on GaAs substrates by metalorganic molecular beam epitaxy (MOMBE). Before the heteroepitaxial growth, atomically flat, As-stabilized GaAs surfaces were prepared by high-temperature As cleaning using tris-dimethylamino-arsenic (TDMAAs). CdSe thin films deposited on (100)ZnSe/GaAs surfaces have been investigated with atomic force microscopy (AFM) and were found to form three-dimensional islands with rather uniform size distribution. A large mismatch (∼7%) of lattice constants between CdSe and ZnSe pseudomorphically grown on GaAs possibly results in the Stranski-Krastanov growth mode. CdSe quantum dots with a diameter of 97±11 nm were successfully formed at 350°C.

In situ selective etching of GaAs for improving (Al)GaAs interfaces using tris-dimethylaminoarsenic

We have investigated the in situ chemical beam etching (CBET) process of (Al)GaAs using tris-dimethylaminoarsenic (TDMAAs) within a chemical beam epitaxy chamber. The optimal CBET condition of (Al)GaAs is established, according to the analysis of atomic force microscopy, capacitance–voltage carrier profiles, and current–voltage (I–V) measurements. This CBET process using TDMAAs is shown to provide a good etching selectivity (&amp;gt;20) of GaAs over AlxGa1−xAs (x⩾0.35) with a very smooth etched surface at the nanometer scale and a clean etched/regrown interface for regrowth applications. Improved I–V characteristics of etched/regrown p-n AlxGa1−xAs (x⩽0.35) junctions is also successfully demonstrated when the GaAs cap layer is preferentially etched first by TDMAAs before regrowth of AlxGa1−xAs.

Improving the etched/regrown GaAs interface by in-situ etching using tris-dimethylaminoarsenic

In this study we have investigated, for the first time, the morphological and electrical properties of the in-situ etched/regrown interfaces of GaAs and Al x Ga 1-x As using tris-dimethylaminoarsenic (TDMAAs) in a chemical beam epitaxy (CBE) chamber. The TDMAAs in-situ etching condition of GaAs is optimized according to the analysis of atomic force microscopy (AFM) and capacitance-voltage (C-V) carrier profiles. The TDMAAs etch rate of GaAs increases from 40 to 135 nm/h by increasing the substrate temperature from 550°C to 700°C, but the etched surface morphology of GaAs on a patterned substrate becomes rougher at higher etching temperatures. A smooth surface morphology of GaAs with an interface state density of 1.4 x 10 11 cm -2 can be obtained at a lower in-situ etching temperature of 550°C. TDMAAs is shown to be an effective and promising precursor for in-situ etching of GaAs, thus providing a clean etched/regrown interface for novel device applications.

Selective area etching of III–V semiconductors using TDMAAs and TDMASb in metalorganic molecular beam epitaxy chamber

Abstract Selective area etching of SiO 2 -masked GaAs using trisdimethylaminoarsenic (TDMAAs) is studied. GaAs substrates are partly masked with stripe shaped SiO 2 films along the [0 1 1] and [0 1 1] directions. Cross-sectional scanning electron microscopy observation shows that the etched shape depends on both the direction of the mask and substrate temperature, and is almost independent of the TDMAAs flow rate. At low substrate temperatures, the (1 1 1)B surface is preferentially formed and a V-shaped groove is formed for the [0 1 1] mask direction. With increasing substrate temperature, the V-groove changes to the channel with vertical side walls due to the drastic increase of the etching rate of (1 1 1)B. For the [0 1 1] mask direction, the vertical (0 1 1) plane is formed at all temperatures. It is found that etched shapes are determined by the difference of etching rates and that etching rates are influenced by the crystal structure on the surface. On the other hand, the etching rate of GaSb by TDMASb is independent of substrate surface orientation. This is because the bond strength of GaSb is weak and the etching proceeds along the direction of molecular beams. Enhanced etching rate is observed for InP by TDMAAs, which is explained by the formation of thin InAs layer on InP due to the irradiation of As released from TDMAAs.

Growth, doping, and etching of GaAs and InGaAs using tris-dimethylaminoarsenic

Growth, doping, and in situ etching of GaAs using cracked and uncracked tris-dimethylaminoarsenic (TDMAAs) in chemical beam epitaxy (CBE) have been studied. A reflection high-energy electron diffraction study indicates that the complete decomposition of TDMAAs occurs below 370 °C. Possible TDMAAs decomposition pathways, which are consistent with experimental data, are presented. The carbon level in undoped GaAs films and the hole concentration in carbon-doped GaAs films using uncracked TDMAAs are much lower than those using cracked TDMAAs, which may be due to atomic hydrogen released from the β-hydride elimination process of uncracked TDMAAs on the GaAs surface. The in situ GaAs etching effect was observed only when the substrate was exposed to uncracked TDMAAs. Possibly, reactive free radicals generated by uncracked TDMAAs on GaAs surfaces are responsible for the etching effect. Surface roughness in selective-area growth of GaAs and the poor interfaces in InGaAs/GaAs multiple quantum wells grown by CBE using uncracked TDMAAs may result from this etching effect.

An evaluation of alternative precursors in chemical beam epitaxy: tris-dimethylaminoarsenic, tris-dimethylaminophosphorus, and tertiarybutylphosphine

In this paper we evaluate the use of tris-dimethylaminoarsenic (TDMAAs), tris-dimethylaminophosphorus (TDMAP), and tertiarybutylphosphine (TBP) as safer alternative sources in CBE. TDMAAs is a viable alternative to arsine for growing GaAs. When In-containing compounds were grown using uncracked TDMAAs or TDMAP with trimethylindium, indiumenhanced TDMAP or TDMAAs desorption was observed, resulting in In droplets on the surface. InP can be grown only if TDMAP is cracked, but many surface defects are observed and the growth rate is very sensitive to the growth temperature. When TBP is used, however, a specular surface can be achieved, and the InP growth rate is independent of substrate temperature from 440 to 480°C. TDMAAs and TDMAP are found to etch GaAs, InP, and GaP, which shows potential applications in in-situ etching and regrowth.

In-Situ Selective Area Etching of GaAs in Metalorganic Molecular Beam Epitaxy Chamber using Trisdimethylaminoarsenic

Selective area etching of GaAs using the metalorganic precursor, trisdimethylaminoarsenic (TDMAAs), is investigated under various etching conditions. The (100)-GaAs surface is partly masked using stripe shaped SiO2 films along the [011] and [0*BAR*1*BAR*1] directions. Cross-sectional scanning electron microscopy (SEM) observation shows that the etched shapes depend on both the stripe mask orientation and the substrate temperature, while they are almost independent of the TDMAAs flow rate and the stripe window width. Excellent mirror surface morphology is achieved at substrate temperatures below 500° C and high TDMAAs flow rates. It is possible to control the etched profiles by choosing etching conditions. TDMAAs is not only a promising arsenic source for growth but is also a quite useful in-situ etching gas source in metalorganic molecular beam epitaxy (MOMBE).