Ben G. Streetman

Resonant-cavity InGaAs-InAlAs avalanche photodiodes with gain-bandwidth product of 290 GHz

We demonstrated a high-speed, resonant-cavity InGaAs-InAlAs separate absorption, charge, and multiplication avalanche photodiode (APD) operating at a wavelength of 1.55 /spl mu/m. Due to the resonant-cavity scheme, these APDs exhibit high external quantum efficiency (/spl sim/70%) and a high unity-gain bandwidth of 24 GHz. Utilizing the excellent noise characteristics of a thin InAlAs multiplication region (k/spl sim/0.18), we have also achieved a gain-bandwidth product of 290 GHz. These bandwidth results are believed to be the highest reported values for APDs operating at 1.55 /spl mu/m.

Resonant-cavity separate absorption, charge and multiplication avalanche photodiodes with high-speed and high gain-bandwidth product

Previously, it has been shown that resonant-cavity separate-absorption-and-multiplication (SAM) avalanche photodiodes (APDs) exhibit high-speed and high gain-bandwidth products. In this letter, we describe a resonant-cavity SAM APD with an additional charge layer that provides better control of the electric field profile. These devices have achieved bandwidths as high as 33 GHz in the low-gain regime and a record gain-bandwidth product of 290 GHz. We also describe the correlation between the gain-bandwidth product and the doping level in the charge layer. With width dependent ionization coefficients, the current versus voltage (I-V) and gain-bandwidth simulations agree well with the measured results and indicate that even higher gain-bandwidth should be achievable with an optimized SACM APD structure.

Low-voltage high-gain resonant-cavity avalanche photodiode

For p-i-n photodiodes and avalanche photodiodes (APDs) in the low-gain regime, there is a performance tradeoff between the transit-time contribution to the bandwidth and the quantum efficiency. A new photodetector structure is demonstrated that alleviates limitations imposed by this tradeoff. This structure utilizes a thin ( approximately=900 AA) depleted absorbing layer to reduce the transit time and achieve avalanche gain at low bias voltage (V/sub b/ approximately=9 V). The external quantum efficiency has been enhanced ( eta /sub e/>49%) by incorporating the structure into a resonant cavity.<<ETX>>

Quantization effects in inversion layers of PMOSFETs on Si (100) substrates

The 2-D hole gas distributions within inversion layers of PMOSFETs have been evaluated by solving the coupled Schrodinger equation and Poisson equation self-consistently based on the effective mass approximation with the light hole and heavy hole subbands taken into account. The threshold voltage shift resulting from the carrier redistribution due to quantization effects is found to be more significant for PMOSFETs than NMOSFETs on (110) Si substrates. For a certain substrate doping concentration the threshold voltage shift from the classical value due to quantization effects is found to be a combination of substrate band bending and oxide potential differences between the classical and the quantum mechanical models.

Low-threshold continuous-wave surface emitting lasers with etched void confinement

Data are presented demonstrating low threshold continuous wave operation of AlAs/GaAs/InGaAs vertical cavity surface emitting lasers. Continuous wave thresholds of 470 /spl mu/A have been realized for device diameters of /spl sim/4 /spl mu/m, and 1.1 mA for a device diameter of 10 /spl mu/m. A two-step molecular beam epitaxial growth process is used which results in a buried etched void surrounding the active cavity of the laser.<<ETX>>

A new transit-time device using quantum-well injection

The use of such techniques as molecular beam epitaxy has allowed the fabrication of devices in which tunneling is the dominant transport mechanism. In this paper a new transit-time device which uses resonant tunneling through a quantum well is proposed and analyzed. Depending on the bias level, this device may permit injection of carriers into the drift region at more favorable phase angles (hence higher efficiencies) than other transit-time devices. The device promises low noise performance and should be capable of operating at high millimeter-wave frequencies with higher output power than other transit-time devices or pure quantum-well oscillators. Since the device uses quantum-well injection and transit-time effects, it is called a QWITT diode.

Quantum-dot resonant-cavity separate absorption, charge, and multiplication avalanche photodiode operating at 1.06 μm

We report on the design, fabrication and performance of a quantum-dot (QD) resonant-cavity separate absorption, charge, and multiplication avalanche photodiode (APD). The device was grown on GaAs using molecular beam epitaxy and was designed to detect light near 1.06 /spl mu/m. The absorbing region consists of a stack of five self-assembled QD layers, that were formed by the deposition of six monolayers of In/sub 0.5/Ga/sub 0.5/As, with GaAs spacer layers. The peak efficiency at 1.06 /spl mu/m is 57% with a spectral bandwidth of 1.3 nm. The photodiode exhibits low dark current, low multiplication noise (k<0.3), good gain characteristics and a low-breakdown voltage (/spl sim/15 V), which is much lower than that of Si-based APDs operating at 1.06 /spl mu/m.

Waveguide In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiode

A high-speed waveguide In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As separate absorption, charge, and multiplication avalanche photodiode suitable for operation at 1.55 /spl mu/m has been demonstrated, a unity-gain bandwidth of 27 GHz was achieved with a gain-bandwidth product of 120 GHz.

Growth of GaNAs by molecular beam expitaxy using a N2/Ar rf plasma

A high efficiency nitrogen rf plasma source has been used to grow GaNAs by diluting the N2 gas with Ar. This source (an EPI UniBulb™ source) was originally designed for use in the growth of pure nitrides at high growth rates. For growth of As-rich GaNAs, high concentrations of active nitrogen lead to the growth of GaN instead of a random alloy. In this work we demonstrate that a dilute N2/Ar mixture leads to GaNAs films where the amount of nitrogen incorporation varies directly with the percentage of N2 in the gas mixture. Films with high structural quality were grown, thus validating the use of this approach.A high efficiency nitrogen rf plasma source has been used to grow GaNAs by diluting the N2 gas with Ar. This source (an EPI UniBulb™ source) was originally designed for use in the growth of pure nitrides at high growth rates. For growth of As-rich GaNAs, high concentrations of active nitrogen lead to the growth of GaN instead of a random alloy. In this work we demonstrate that a dilute N2/Ar mixture leads to GaNAs films where the amount of nitrogen incorporation varies directly with the percentage of N2 in the gas mixture. Films with high structural quality were grown, thus validating the use of this approach.

Ambient‐induced surface effects on InP and GaAs

The effects of gas ambient changes on the photoluminescence (PL) intensity and the conductivity of chemically cleaned (100) InP and GaAs have been investigated. The room‐temperature PL intensity of n‐type, p‐type, and Fe‐doped semi‐insulating InP is found to be reversibly changed by the presence of various gases at the semiconductor surface. The resistivity of thin‐film InP resistors is also found to be affected by gas ambient changes, both under illumination and in the dark. These measurements show that the surface Fermi level of InP is not tightly pinned and is reversibly changed by exposure to different ambients. The PL intensity and surface conductivity of GaAs are also found to be sensitive to the gas environment, though to a lesser degree than InP. The responses of InP and GaAs are of a different nature and suggest that the surface state densities of these materials are reversibly affected by the chemisorption of oxygen. This in turn suggests that there are adsorbate‐induced surface states on InP an...