Hideyasu Ando

Metalorganic molecular‐beam epitaxy of ZnSe and ZnS

The metalorganic molecular‐beam epitaxial growth of ZnSe and ZnS on (100) GaAs has been demonstrated and characterized. Diethylzinc and diethylselenide were used for the ZnSe growth, while for the ZnS growth both hydrogen sulfide and diethylsulfide (DES) were tested as sulfur sources. The dependence of the growth rate on various growth conditions was investigated to clarify the growth mechanism. When group VI alkyls were used as sources, pyrolysis in a cracking cell was required, unlike metalorganic chemical vapor deposition. Interesting differences in growth kinetics and in crystallinity between H2S‐based and DES‐based ZnS have been found. Photoluminescence spectra of ZnSe layers measured at 4.2 K showed resolved exciton emissions. However, donor‐acceptor pair emission lines attributed to a Li acceptor (LiZn) were also observed. Smooth, monocrystalline ZnS layers could be grown at substrate temperatures above 250 °C by using cracked H2S and DES, and above 150 °C by using uncracked H2S. Photoluminescence ...

Metalorganic molecular beam epitaxial growth of ZnSe using diethylzinc and diethylselenide

ZnSe epitaxial layers have been grown for the first time on (100) GaAs substrates by metalorganic molecular beam epitaxy using diethylzinc and diethylselenide. Diethylselenide is cracked by the cracking furnace. Smooth single-crystalline layers can be grown at substrate temperatures above 200°C. Photoluminescence spectra vary noticeably with the substrate temperature. Above 400°C, the spectra measured at 71 K were dominated by intense blue donor-acceptor pair bands, and broad luminescence bands at longer wavelengths were weak.

Metalorganic gas control system for gas source molecular beam epitaxy

We have developed a new method to precisely control the small mass flow of low vapor pressure gases without a carrier gas in gas source molecular beam epitaxy. Group III metalorganic gases (TEA1, TEIn, and TEGa) were controlled by measuring the pressure difference at the flow element and giving feedback to the control valve. The beam pressure of source gases monitored at the growth position in a molecular beam epitaxy growth chamber had good linearity with the pressure difference at both sides of the flow element. The beam pressure was controlled with a maximum deviation of 2% for over 1 h of operation. The response of the beam pressure to changes in flow rate was quick with neither overshoot nor undershoot. The beam pressure could be reduced to 1/5 of its initial value in less than 5 s and then restored in less than 3 s. The source gases could be switched on and off abruptly. The rise time to 90% of the saturated beam pressure was less than 1 s and fall time to 10% of the saturated beam pressure was betw...

Gas Source MBE Growth of GaAs/AlGaAs Heterojunction Bipolar Transistor with a Carbon Doped Base Using Only Gaseous Sources

We report on the first growth of a GaAs/Al0.2Ga0.8As heterojunction bipolar transistor by gas source MBE using only gaseous sources. The p-type GaAs base layer was carbon doped using trimethylgallium (p=4×1019 cm-3) and the n-type Al0.2Ga0.8As emitter layer was silicon doped (n=9×1017 cm-3) using uncracked disilane. A dc current gain of 40 was obtained at a current density of 50 A/cm2.

Carbon-Doped-Base AlGaAs/GaAs HBTs Grown by Gas-Source Molecular Beam Epitaxy Using Only Gaseous Sources

We report the fabrication and electrical characteristics of carbon-doped-base AlGaAs/GaAs heterojunction bipolar transistors (HBTs) grown by gas-source molecular beam epitaxy (GSMBE) using only gaseous sources. The base of HBTs is compositionally uniform and doped with carbon to a carrier concentration of 4×1019 cm-3. A current gain of 45 was obtained at a collector current density of 4×104 A/cm2. These HBTs were electrically stable under current stress, as confirmed by current gain and Gummel plots.

A study of cold dopant sources for gas source MBE : the use of disilane as an N-type dopant of AlxGa1-xAs (x = 0-0.28) and trimethylgallium as a P-type dopant of GaAs

Disilane (Si2H6) was shown to be a suitable n-type gaseous dopant source for the gas source MBE (GSMBE) growth of AlxGa1-xAs (x=0–0.28) using arsine, triethylgallium and triethylaluminium as host material sources. The carrier concentration of the AlxGa1-xAs epilayer was controlled between 5×1017–2×1018 cm-3 (x=0–0.28) by varying the Si2H6 flow rate from 0.3 to 10 sccm. Furthermore, the hole concentration of GaAs grown using trimethylgallium as both the dopant and also the host material source, was controlled from 1.3×1020 to 6.3×1018 cm-3 by varying the V/III ratio from 0.5 to 6.5.

High current gain AlGaAs/GaAs heterojunction bipolar transistors with carbon-doped base grown by gas source molecular beam epitaxy using trimethylamine alane as the aluminum source

We report on AlGaAs/GaAs heterojunction bipolar transistors (HBTs) with a 70 nm-wide 3.4×1019 cm-3 carbon-doped base, grown by gas-source molecular beam epitaxy (GSMBE) using trimethylamine alane (TMAAl) as the aluminum source. We reduced the residual carbon concentration of the AlGaAs emitter layer to less than the secondary ion mass spectroscopy (SIMS) detection limit (1×1016 cm-3) by optimizing the overall growth conditions. The DC current gain of 160, obtained at a current density of 3×104 A/cm2, is the highest value ever reported for GSMBE-grown AlGaAs/GaAs HBTs.

Gas Source Melecular Beam Epitaxy Growth of High Quality AlGaAs Using Trimethylamine Alane as the Aluminum Source

We investigated the dependence of the background impurity incorporation on growth conditions and optical properties of undoped AlGaAs grown by gas source molecular beam epitaxy using trimethylamine alane (TMAAl), triethylgallium, and arsine. The use of TMAAl enabled us to reduce the carbon concentration (7×1016 cm-3) to over one order of magnitude less than that using triethylaluminum (TEAl). The 77 K photoluminescence spectrum of undoped AlGaAs grown using TMAAl was dominated by excitonic band-edge emission not observable in AlGaAs grown using TEAl. Furthermore, we report for the first time the doping characteristics of n-type AlGaAs grown using disilane (Si2H6) as an n-type gaseous dopant source together with TMAAl. The carrier concentration (5×1017-3×1018 cm-3) in n-AlxGa1-xAs (x=0.09-0.27) was reliably controlled and showed the same Si2H6 flow rate dependence as that of GaAs. The activation efficiency of silicon was more than 60%. We demonstrated the excellent n-type doping characteristics by uisng TMAAl.

Si doping of AlGaAs using Si2H6 grown by gas‐source molecular‐beam epitaxy using trimethylamine alane, triethylgallium, and AsH3

We investigated Si doping characteristics and background oxygen and carbon impurity incorporation in gas‐source molecular‐beam epitaxy grown n‐AlGaAs as a function of the AlAs mole fraction, x, using uncracked Si2H6 as the cold gaseous dopant source and trimethylamine alane, triethylgallium, and AsH3 as host constituent sources. The carrier concentration of n‐AlGaAs showed a linear dependence on the Si atomic concentration in the x range from 0 (GaAs) to 0.40. The activation efficiency of Si in the n‐AlGaAs films was more than 60% in the carrier concentration range of 1.5 × 1017–3 × 1018 cm−3. The oxygen concentration was in the range of 3–4 × 1017 cm−3 which is insensitive to x, and the carbon concentration increased gradually from 4 to 7 × 1016 cm−3 with increasing x in the range of 0.09–0.40.

Doping Characteristics of Gas-Source MBE-Grown n-AlxGa1-xAs (x=0-0.28) Doped Using Disilane

Si doping using uncracked disilane (Si2H6) in gas-source molecular beam epitaxy of n-AlxGa1-xAs (x=0-0.28) using triethyl gallium, triethyl aluminum, and arsine was studied in a carrier concentration from 5 × 1017 to 2 × 1018 cm-3. We found that (1) the Si atomic concentration of AlGaAs is proportional to the Si2H6 flow rate, and decreases with increasing Al content at a constant Si2H6 flow rate, and (2) the carrier concentration of AlGaAs shows a square-root dependence on the Si atomic concentration incorporated.