Planar-doped Structures Research Articles

MBE growth and transport properties of silicon δ-doped GaAs/AlAs quantum well structures for terahertz frequency detection

We present the electrical characterization of n-type GaAs/AlAs multiple quantum well (MQW) structures designed for terahertz (THz) radiation sensing at cryogenic temperatures. The samples were grown by solid source molecular beam epitaxy (MBE) and were δ-doped with silicon atoms at each potential well center. Temperature dependent Hall effect data show that (i) the conduction in these planar doped structures is thermally activated below 180 K, (ii) the free carriers sheet densities are near the metal–insulator transition, and (iii) the low temperature mobility is controlled by ionized impurities scattering. The study of the magneto-transport properties at 1.3 K further indicates that only the fundamental electronic sub-band of the two-dimensional electronic gas is populated. The MQW samples were then processed into lateral mesa-shaped photodetectors to investigate their spectral response in the THz frequency range. The preliminary experimental results for the proposed detection scheme, which involves transitions in the confined shallow donor impurity states, are described.

Quantum-well reshaping by hot electrons in planar-doped structures

The self-consistent calculations of the potential well in a planar-doped semiconductor demonstrate that carrier heating in strong electric fields leads not only to a repopulation of the two-dimensional carriers between the subbands but also to a significant deepening and broadening of the quantum well, which is accompanied by a change of the subband energies consequently. The important role of such a change is confirmed by the particularities of the formation of metastable ${\mathrm{DX}}^{\ensuremath{-}}$ centers in planar-doped GaAs:Si.

The Effect of Rapid Thermal Annealing on the Electrical and Material Characteristics of Planar Doped and Uniformly Doped GaAs/AiGaAs/InGaAs Pseudomorphic HEMT Structures

ABSTRACTMBE grown GaAs/Al0.25Ga0.75As/In0.85Ga0.85 As structures were subjected to SiNx capped rapid thermal annealing and their electrical and material properties were characterized by Hall measurements and photoluminescence (PL). Low temperature (5°K) PL spectra from undoped structures annealed up to 900°C indicated negligible intermixing at the AIGaAs/lnGaAs interface. For planar doped structures (Nd≈5×1012/cm2) the Hall mobility began to decrease at anneal temperatures as low as 800°C with significant degradation observed for annealing temperatures at 850°C. This data is supported by PL spectra which indicate no significant change for samples annealed at 800°C. For the samples annealed at ≥ 850°C a large increase in the full width at half maximum of the transitions from the electron sub-bands of the InGaAs quantum well were observed, suggesting that the change in electrical characteristics is primarily due to diffusion of the Si doping pulse. In contrast. Hall measurement of uniformly doped structures reveal only small decreases in mobility and no significant change in sheet concentration for anneal temperatures up to 900°C and doping levels up to 2.5×1018/cm3. PL spectra reveal no structural changes.

Atomic layer epitaxy of planar-doped structures for nonalloyed contacts and field-effect transistor

Atomic layer epitaxy has been used for the low-temperature deposition of planar-doped structures using organometallic sources AsH3 and H2Se. Carrier concentration in the 1019/cm3 range was achieved, with a sharp concentration profile comparable to the best reported for equivalent structures by molecular beam epitaxy. A set of planar-doped Se sheets, separated by 50 Å of GaAs, was used for nonalloyed contacting layers to n-GaAs films with contact resistivity in the low 10−6 Ω cm2 range. Finally, a planar-doped field-effect transistor (FET) was fabricated with planar-doped sidewall source and drain contacting layers, giving a performance comparable to that of reported planar-doped structures by other techniques. This is considered to be the first demonstration of a planar-doped FET using organometallic sources.

Electrical and Material Characterization of the Stability of ALGaAs and GaAs Planar Doped Structures

AbstractIn this work we have studied the effects of silicon planar doping on the electrical and optical properties of GaAs, and the effects of rapid thermal annealing on AIGaAs planar-doped structures. MBE-grown GaAs epilayers with multiple planar-doped layers displayed a 1.2 eV photoluminescence peak, presumably due to gallium vacancy - donor complexes, for samples with nominal silicon sheet densities much greater than measured charge densities. The Hall mobilities of these samples were also reduced compared to both uniformly-doped and planar-doped structures whose silicon areal densities were more nearly equal to measured sheet charge densities, although X-Ray rocking curves were nearly identical in all cases. Planar-doped AIGaAs Schottky diodes had nearly ideal electrical characteristics. Rapid thermal annealing of the planar-doped structures before fabrication increased the diode ideality factor from n=1.06 to n=1.60, seriously degraded the saturation current and breakdown voltage, and increased the doping profile FWHM from 60Å to 170Å.

Electrical and Material Characterization of the Stability of ALGaAs and GaAs Planar Doped Structures

AbstractIn this work we have studied the effects of silicon planar doping on the electrical and optical properties of GaAs, and the effects of rapid thermal annealing on AIGaAs planar-doped structures. MBE-grown GaAs epilayers with multiple planar-doped layers displayed a 1.2 eV photoluminescence peak, presumably due to gallium vacancy - donor complexes, for samples with nominal silicon sheet densities much greater than measured charge densities. The Hall mobilities of these samples were also reduced compared to both uniformly-doped and planar-doped structures whose silicon areal densities were more nearly equal to measured sheet charge densities, although X-Ray rocking curves were nearly identical in all cases. Planar-doped AIGaAs Schottky diodes had nearly ideal electrical characteristics. Rapid thermal annealing of the planar-doped structures before fabrication increased the diode ideality factor from n=1.06 to n=1.60, seriously degraded the saturation current and breakdown voltage, and increased the doping profile FWHM from 60Å to 170Å.