摘要:

Roles of an ultrathin Si insertion layer in AlAs/Si/GaAs system are studied by usinginsitux‐ray photoemission spectroscopy. It is found that a main role of the Si layer is not a control of a valence band offset as was proposed by Sorbaetal., but an introduction of band bending in an overgrown layer. The proposed band‐bending model explains all the experimental observations in the x‐ray photoemission spectra; an Al 2pline broadening and the dependence of a peak energy shift on the crystallographic orientation and an overgrown‐layer thickness.

ISSN:0734-211X    

DOI:10.1116/1.587168

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Metal–insulator–semiconductor (MIS) field effect transistors were fabricated on InP substrates using a planar self‐aligned gate process. A 700–1000 Å gate insulator of SiO2doped with phosphorus was deposited by a direct plasma enhanced chemical vapor deposition at 400 mTorr, 275 °C, 5 W, and power density of 8.5 mW/cm2. High frequency capacitance–voltage measurements were taken on MIS capacitors which have been subjected to a 700 °C anneal and an interface state density of 1×1011/eV cm2was found. Current–voltage measurements of the capacitors show a breakdown voltage of 107V/cm and a insulator resistivity of 1014Ω cm. Transistors were fabricated on semi‐insulating InP using a standard planar self‐aligned gate process in which the gate insulator was subjected to an ion implantation activation anneal of 700 °C. MIS field effect transistors gave a maximum extrinsic transconductance of 23 mS/mm for a gate length of 3 μm. The drain current drift saturated at 87.5% of the initial current, while reaching to within 1% of the saturated value after only 1×103. This is the first reported viable planar InP self‐aligned gate transistor process reported to date.

ISSN:0734-211X    

DOI:10.1116/1.587169

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The photoluminescence (PL) spectral shape and position from single, modulation doped, and undoped AlGaAs/InGaAs/GaAs quantum wells have been studied at room temperature (RT) with the purpose of evaluating the usefulness of the PL technique for verifying device material structures. Starting with a general expression for the line shape, we can qualitatively predict the spectral shape and position by evaluation of the squared overlap integrals of the four possible transitions between the two lowest states in the valence and conduction band wells. A self‐consistent calculation is used to determine the equilibrium wave functions and the energies of the bound states in the quantum well. Good agreement is found between the experimental and theoretical peak positions, and the Stark shift in the low‐energy spectral onset between doped and undoped structures also can be closely reproduced. The accuracy of the calculations has been verified by comparing structures with varying layer widths and constant In composition, and vice versa. We demonstrate that the doping‐induced electric field in the quantum well strongly affects the spectral shape of the PL signal. In fact, the dominant transition is typically from the first excited conduction band state to the valence band ground state. A sensitivity analysis restricted to the square of the overlap integrals and the peak wavelengths shows that changes in the quantum well parameters induced by changing the Ga and In fluxes can be separated for InGaAs mole fractions typically used in devices. This has also been verified by experiment.

ISSN:0734-211X    

DOI:10.1116/1.587170

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The diode diameter dependence of current density in mesap–njunctions was used to measure surface recombination velocities (S) for both InGaP and AlGaAs. For InGaP,Svalues of 4–5×104cm s−1were obtained for both wet‐ and dry‐etched mesas, and the surface was relatively insensitive to changes resulting from annealing or plasma exposure. Surface passivation by (NH4)2Sxtreatment reduced the recombination velocity by a factor of 2. By contrast, AlGaAs displayed a strong sensitivity to the type of processing steps used in photonic and electronic device fabrication, with values ofSas high as 9×105cm s−1after low temperature annealing, and as low as 3.7×104cm s−1after sulphide passivation.

ISSN:0734-211X    

DOI:10.1116/1.587171

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The influence of HF (5%) on the surface of GaAs (100) and the oxidation of HF treated samples in laboratory air have been investigated by x‐ray photoelectron spectroscopy, angle‐resolved monochromatized photoelectron spectroscopy, and time‐of‐flight secondary ion mass spectroscopy. Etching with HF does not only remove the oxide but leads to an increasing loss of Ga from the surface. After some minutes a layer of elemental As is formed which grows linearly with the logarithm of HF storage time. Subsequent oxidation starts with the formation of As2O3and Ga2O3, with preferential oxidation of As. After some hours, higher oxidized states of As and Ga [As2O5, GaAsO4, Ga(OH)3] are formed under the influence of light. The rate of As oxidation decreases until a state is reached which consists of nearly equal amounts of As and Ga. For storage times less than one week, the oxide thickness increases linearly with the logarithm of storage time, which is consistent with the Cabrera–Mott mechanism found earlier for the oxidation of GaAs.

ISSN:0734-211X    

DOI:10.1116/1.587172

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

A series of GaAs/In0.25Ga0.75As/GaAs pseudomorphic high electron mobility transistors (HEMTs) was grown by low‐pressure metalorganic chemical vapor deposition. The respective influences of δ‐doping time and spacer thickness on the two‐dimensional electron gas concentrations and the mobilities were studied. The maximum mobilities, μ=5600 and 22 000 cm2/V s at 300 and 77 K, respectively, appeared at a spacer thickness of 100 Å with a δ‐doping time of 0.2 min. A δ‐doped GaAs/In0.25Ga0.75As/GaAs pseudomorphic HEMT with the above parameters was fabricated. This device revealed high saturation current density of 350 mA/mm, transconductance of 95 mS/mm, and broad maximum transconductance region of 2.5 V with geometry of 2×100 μm2at room temperature. In addition, very high breakdown voltage (26 V) and low leakage current (≤2 μA at −26 V) were achieved.

ISSN:0734-211X    

DOI:10.1116/1.587174

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Finely focused beams of silicon ions have been used to produce novel three‐dimensional doping profiles in GaAs metal–semiconductor field effect transistor channels. The structure studied is a GaAs field effect transistor in which the channel consists of conducting stripes in a semi‐insulating substrate, with the doping profile graded to give a step change in the doping density under the gate. The striped channel has the effect of increasing the device transconductance, while the longitudinal dopant grading increases the gate breakdown voltage. Striped and stepped‐channel devices are compared with devices with uniform channels and with striped nonstepped channels; improved performance is demonstrated.

ISSN:0734-211X    

DOI:10.1116/1.587175

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

Regions of light‐emitting porous silicon fabricated by anodic electrochemical etching have been patterned by photolithography. Samples were spin‐coated with photoresist, and contact photolithography was used to define the desired mask pattern. Exposure of unmasked sample regions to an isotropic oxygen plasma in a barrel reactor results in a dramatic reduction of the visible photoluminescence. The resulting patterns exhibit high contrast, with a minimum feature size of 4 μm. The patterns are remarkably stable, withstanding both chemical treatment and atmospheric contamination.

ISSN:0734-211X    

DOI:10.1116/1.587176

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The achievement of ultra‐shallow doping profiles by ion implantation requires low energy implants and minimum thermal budgets. In this case, the profile is generally more sensitive to the implant parameters, including implant angles and dose. A detailed study has been performed of the dependence of boron and arsenic profiles on tilt angle, rotation angle, and dose for energies down to 15 keV for BF+2and As+implants in (100) Si wafers. The major axial and planar channels have been determined using critical angle analysis and are in agreement with experimental observations. In addition, computationally efficient models have been developed for BF2and As implants which accurately account for the boron and arsenic profile dependence on tilt angle, rotation angle, and dose in addition to energy.

ISSN:0734-211X    

DOI:10.1116/1.587177

出版商:American Vacuum Society    

年代:1994

数据来源: AIP

摘要:

The simulation, fabrication, and characterization of ultra‐shallow‐doped films are critical to optimizing sub‐half‐micron devices. This article describes key metal–oxide–semiconductor field effect transistor elements and their impact on device performance, emphasizing the need for ultra‐shallow‐doped films. Methods to achieve such small geometries are discussed. Future technology trends are projected. These trends are evolving at a fast pace, requiring improved simulation tools and novel measurement methods. Simulated structures are used to define device needs for abrupt composition profiles and to highlight the stringent requirements that are imposed on film characterization and model verification.

ISSN:0734-211X    

DOI:10.1116/1.587178

出版商:American Vacuum Society    

年代:1994

数据来源: AIP