PIN Diode Structure Research Articles

Fabrication of low-loss SOI nano-waveguides including BEOL processes for nonlinear applications

We report successful fabrication of low-loss SOI nano-waveguides with integrated PIN diode structures. The entire fabrication process is done on a 200 mm BiCMOS toolset using front-end-of-line (FEOL) and back-end-of-line (BEOL) processes and does not show any undesirable influence upon the photonic performance. Such a waveguide technology forms an attractive platform for a wide range of nonlinear applications due to efficient free carrier removal as well as use of standard substrates and processing technology. Nonlinear experiments were conducted to investigate the potential of the introduced technology. The performance of the designed waveguides can be used as a benchmark for future development of proposed platform for integrated silicon photonics and electronics circuits.

Electro-thermal analysis and optimization of edge termination of power diode supported by 2D numerical modeling and simulation

High reliability and performance of power semiconductor devices depend on an optimized design based on a good understanding of their electro-thermal behavior and of the influence of parasitic components on their operation. This leads to the need for electro-thermal 2/3-D numerical modeling and simulation in power electronics as an efficient tool for analysis and optimization of device structure design and identification of critical regions. In this paper we present an analysis and geometry optimization of a high power pin diode structure supported by advanced 2-D mixed mode electro-thermal device and circuit simulation. Lowering of the operation temperature by better power management and heat dissipation due to an optimized structure design will allow withstanding higher current pulses and suppressing the damage of the analyzed structure by thermal breakdown.

Study of variations of the carrier recombination and charge transport parameters during proton irradiation of silicon pin diode structures

Techniques for the remote and in situ control of carrier recombination and drift parameters during proton irradiation are presented. The measurement and evaluation of the carrier recombination and drift-diffusion characteristics are based on simultaneous analysis of microwave probed photoconductivity transients and of the induced charge collection current transients in diodes with applied electric field during the proton exposure.

Combined Electromagnetic and Drift Diffusion Models for Microwave Semiconductor Device

In this work, we present a numerical model to solve the drift diffusion equations coupled with electromagnetic model, where all simulations codes are implemented using MATLAB code software. As first, we present a one-dimensional (1-D) PIN diode structure simulation achieved by solving the drift diffusion model (DDM). Backward Euler algorithm is used for the discretization of the proposed model. The aim is to accomplish time-domain integration. Also, finite different method (FDM) is considered to achieve space-Domain mesh. We introduced an iterative scheme to solve the obtained matrix systems, which combines the Gummel’s iteration with an efficient direct numerical UMFPACK method. The obtained solutions of the proposed algorithm provide the time and space distribution of the unknown functions like electrostatic potential and carrier’s concentration for the PIN diode. As second case, the finite-difference time-domain (FDTD) technique is adopted to analyze the entire 3-D structure of the stripline circuit including the lumped element PIN diode. The microwave circuit is located in an unbounded medium, requiring absorbing boundaries to avoid nonphysical reflections. Active device results were presented and show a good agreement with other reference. Electromagnetic results are qualitatively in agreement with other results obtained using SILVACO-TCAD.

Investigation of a contacting scheme for self-assembled cleaved edge overgrown InAs nanowires and quantum dot arrays

The expanding of research in nano-scale systems is essentially driven by interest in the fun-damental physical properties of solid state matter at the nanoscale and the hope to apply them to novel technologi-cal devices. With self-assembled (bottom-up approach) nanostructures it is possible to achieve even smaller sized structures in combination with top-down technologies and allow at the same time a high control of the size distribu-tion. An example for such materials are defect free semi-conductor QDs grown by MBE or CVD processes [1]. Es-pecially III–V self-assembled QDs, e.g. InGaAs QDs, are subject to intense investigations due to their superior opti-cal properties. These systems are interesting due to promis-ing applications, like single photon sources, lasing, optical amplifiers or solar cells [2–4]. For this reason it is interest-ing to characterize the electronic properties of self-assembled nanostructures. Ensembles of QDs can be con-tacted by embedding the QDs film into a pin-diode struc-ture. However to address single or a small ensemble of nanostructures still represents a challenging task. In several previous publications the promising approach of self-assembled InAs nanostructures obtained by cleaved edge overgrowth was presented [5, 6]. Again the optical proper-ties are easily accessible [7], but for further investigations a direct injection of charge carriers into the nanostructures is interesting. Previous pioneering work has shown how CEO structures can be used for low-dimensional transport at the cleavage plane first in GaAs quantum wires [8] and more recently in AlAs quantum wires [9]. At this point we would like to shortly review the technique of self-assembled InAs nanostructure growth. The procedure re-lies on the fact that the three-dimensional InAs layer

Suppression of Edge Recombination in InAs/InGaAs DWELL Solar Cells

AbstractThe InAs/InGaAs DWELL solar cell grown by MBE is a standard pin diode structure with six layers of InAs QDs embedded in InGaAs quantum wells placed within a 200-nm intrinsic GaAs region. The GaAs control wafer consists of the same pin configuration but without the DWELL structure. The typical DWELL solar cell exhibits higher short current density while maintaining nearly the same open-circuit voltage for different scales, and the advantage of higher short current density is more obvious in the smaller cells. In contrast, the smaller size cells, which have a higher perimeter to area ratio, make edge recombination current dominant in the GaAs control cells, and thus their open circuit voltage and efficiency severely degrade. The open-circuit voltage and efficiency under AM1.5G of the GaAs control cell decrease from 0.914V and 8.85% to 0.834V and 7.41%, respectively, as the size shrinks from 5*5mm2 to 2*2mm2, compared to the increase from 0.665V and 7.04% to 0.675V and 8.17%, respectively, in the DWELL solar cells. The lower open-circuit voltage in the smaller GaAs control cells is caused by strong Shockley-Read-Hall (SRH) recombination on the perimeter, which leads to a shoulder in the semi-logarithmic dark IV curve. However, despite the fact that the DWELL and GaAs control cells were processed simultaneously, the shoulders on the dark IV curve disappear in all the DWELL cells over the whole processed wafer. As has been discussed in previous research on transport in QDs, it is believed that the DWELL cells inhibit lateral diffusion current and thus edge recombination by collection first in the InGaAs quantum well and then trapping in the embedded InAs dots. This conclusion is further supported by the almost constant current densities of the different area DWELL devices as a function of voltage.

A New Approach of Electronics and Photonics Convergence on Si CMOS Platform: How to Reduce Device Diversity of Photonics for Integration

Integrated photonics via Si CMOS technology has been a strategic area since electronics and photonics convergence should be the next platform for information technology. The platform is recently referred to as “Si photonics” that attracts much interest of researchers in industries as well as academia in the world. The main goal of Si Photonics is currently to reduce material diversity of photonic devices to pursuing CMOS-compatibility. In contrast, the present paper proposes another route of Si Photonics, reducing diversity of photonic devices. The proposed device unifying functionality of photonics is a microresonator with a pin diode structure that enables the Purcell effect and Franz-Keldysh effect to emit and to modulate light from SiGe alloys.

High speed germanium detectors on Si

AbstractAll the common group IV semiconductors – diamond, silicon carbide, silicon, germanium‐ are indirect semiconductors which narrows their optoelectronic application width. Silicon itself has a room temperature band gap of 1.12 eV with the first direct transition at 3.4 eV delivering strong absorption in the ultraviolet and the weaker indirect absorption in the visible up to the near infrared λ = 1.1 µm. Ge has a smaller bandgap (0.66 eV) which correlates with a larger band to band absorption limit (1.9 eV) but even more important the direct transition (0.8 eV) comes down to only about 150 meV above the indirect one. The speed of photodetectors is limited by two main factors, the carrier transport within the device and the RC time constant from loading the depletion layer capacitance via the external supply. High speed operation is obtained with absorption in the depletion layer where high electric fields accelerate the carriers to saturation velocity and avoiding slow carrier diffusion. In a pin diode structure this is obtained by sharp doping profiles (orders of magnitude increase/decrease within several Nanometers) and by the misfit dislocation network of the virtual substrate blocking diffusion from below the device. Indeed within a very short time the bandwidth of Ge on Si detectors was shifted in the GHz regime. The operation bias is usually in the reverse direction, but our group demonstrated also high speed (25 GHz) with zero bias when dark currents should be minimized. These photodetectors are sensitive in a broad spectral range (from visible to 1.6 µm). The lower limit is given by the absorption in the cap layer; the upper limit is the direct absorption edge of Ge. Silicon on insulator (SOI) optical waveguide system concept is explained which uses a light signal externally coupled in the silicon circuit. For its simplicity we propose a silicon on insulator (SOI) substrate. Rectangular waveguides like rib or ridge waveguides provide strong optical confinement at low device fabrication requirements. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Material properties and performance of metamorphic optoelectronic integrated circuits grown by molecular beam epitaxy on GaAs substrates

Solid source molecular beam epitaxy was used to deposit in a continuous process an integrated metamorphic high electron mobility transistor (HEMT) and PIN photodiode structure. A metamorphic buffer layer was first grown on a GaAs substrate to expand the lattice constant to that of In0.53Ga0.47As used in the device layers. The HEMT layers were subsequently grown followed by the PIN diode structure. Cross-sectional and plan-view transmission electron micrographs showed planar layer interfaces and a dislocation density in the device layers of 1×106 cm−2. The device characteristics of the HEMT transistors were not adversely affected by growth of the PIN structure on top. Also the bandwidth and responsivity of the metamorphic PIN photodiode were comparable to an InP PIN photodiode with similar dark currents. The integrated HEMT/PIN diode circuit had a 3 dB bandwidth 20% greater than a hybrid combination of devices due to a decrease in parasitic losses from device interconnects. The frequency performances of circuits fabricated from the same wafer exhibited a high degree of uniformity.

Electro-absorption and electro-refraction in InGaAsN quantum well structures

The first observation of electro-absorption in a InGaAsN-GaAs single quantum well pin-diode structure is reported. Clear excitonic resonances were observed at room temperature at 1150 nm and a strong Stark shift is obtained for applied fields of up to 2.6×107 V/m. The field induced changes in refractive index were calculated at 1300 and 1550 nm and it is concluded that low voltage phase modulators could be fabricated using this material.

Overshoot velocity in ultra-broadband THz studies in GaAs and InP

We model velocity overshoot in GaAs and InP using a fullband, particle-based device simulator based on the so-called cellular automaton method. This study has been motivated by the recent availability of experimental measures of the THz radiation generated by transient acceleration of photogenerated charge carriers in pin diode structures. The fullband code used in this study includes the full energy-momentum dispersion relation of electrons and holes as well as the full dispersion for the relevant phonons. Here we use this code for the simulation of high-field transient transport in bulk GaAs, InP, and for the experimental pin structure, where favorable comparison is found with the velocities measured from the transient THz radiation after ultrafast excitation.

High performance gated lateral polysilicon PIN diodes

This paper investigates the characteristics of high performance lateral polysilicon diodes. Low leakage currents and high ON currents were achieved using a gated PIN diode structure. An independent control gate terminal was placed over the intrinsic region of the diodes to improve the properties of the polysilicon diodes. The addition of the control gate was found to improve both the ON resistance and the leakage current by an order of magnitude. The gated PIN diodes had leakage currents less than 0.05 pA μm −1 width at 5 V of reverse bias, and ON resistance less than 1 MΩ μm −1 width for an intrinsic region length of 2 μm. A gated PIN diode model is presented that models the diode as an ideal diode in series with a thin film transistor. This model is used to explain the impact of the control gate on the ON resistance and the leakage current of the gated PIN lateral polysilicon diodes.

Stacked PIN diode structures for microwave switching

A diode structure consisting of several stacked PIN diodes with tunnel junctions serving as quasi-Ohmic intercontacts is proposed. This structure is preferable if a microwave switch is required to have both high breakdown voltage and very small switching time. In this case a conventional (single-base) PIN switch has too large forward voltage drop across the base at sufficiently high current densities, because the base length is much greater than the bipolar diffusion length. This leads to high electric fields in the base and the development of unwelcome hot-electron effects. The replacement of the long base with several narrow bases connected in series by heavily doped p +n + tunnel inserts solves this problem effectively. Direct numerical calculations have shown that this stacked structure exhibits a substantially smaller DC forward voltage drop at the same switching times (or substantially smaller switching times at the same DC forward voltage drops). At the microwave frequency range, the resistance of the stacked structure can be decreased drastically because all the newly formed pn-junctions are shorted by their large capacitances.

Properties of Image Sensor Structure Obtained Below 120°C On The Foil By Reactive Magnetron Sputtering

ABSTRACTPolyimide substrates are of interest because of their thermal stability, light weight, and good mechanical characteristics. This paper reports thermal control multilayer deposition experiments which have strongly affected the properties of the image sensor structure (TFT + photodiode). Particularly TFT properties have been studied with respect to difficulties of obtaining of good quality a-SiNx:H films at temperature below 120°C. We characterize the structural properties using infrared absorption, refractive index measurements, small angle x-ray diffraction and the optoelectrical measurements of the TFT and PIN diode structure. The linear image sensor consisting of two rows, 40 pixels per row, with dimensions 0.6 mm2was made on the polyimide foil.

Low Temperature Grown Thin Inalas Step Graded Buffers for Application on Optical Modulator at 1.3 μM

ABSTRACTPreliminary results are described about the growth, structure and properties of multiple quantum well(MQW) Quantum Confined Stark Effect (QCSE) modulators grown on GaAs substrates for operation at 1.3μm in wavelength. Step graded InAlAs buffer layers grown at low temperature by molecular beam epitaxy (MBE) with a total thickness of 0.3 μm are used to relieve the strain caused by the lattice-mismatch between the GaAs substrate and the In0.35Ga0.65As/In0.35Al0.65As MQW heterostructure. X-ray diffraction spectra show that significant lattice relaxation takes place in the buffer. A quantum confined Stark shift of the exciton absorption peak of 48meV was obtained with an applied electric field of 130KV/cm, measured in PIN diode structures consisting of 30 period 95ÅIn0.35Ga0.65As/100ÅIn0.35Al0.65As MQWs on a 3 stage compositionally step graded InxAl1−xAs buffer doped with Si to 5*1017/cm3 grown on a nominally 1018/cm3 n-type doped GaAs substrate.

Growth and characterization of (111)B InGaAs/GaAs multi-quantum well PIN diode structures

High quality piezoelectric strained InGaAs/GaAs multi-quantum well structures on (111)B GaAs substrates have been grown by solid-source molecular beam epitaxy in a PIN configuration. 10K photoluminescence (PL) shows narrow peaks with widths as low as 3 meV for a 25-period structure while room temperature (RT) PL shows several higher order peaks, normally forbidden, indicating breaking of inversion symmetry by the piezoelectric field. Furthermore, both the 10K PL peak position and the form of the RT PL spectra depend on the number of quantum wells within the intrinsic region, suggesting that the electric-field distribution is altered thereby. Diodes fabricated from these structures had sharp avalanche breakdown voltages (Vbd) and leakage currents as low as 8 × 10−6 A/cm2 at 0.95 Vbd, indicating quality as high as in (100) devices.

Optical waveguide switches in silicon based on Ge-indiffused waveguides

An optical waveguide switch based on single-moded Ge-indiffused waveguides with a lateral pin-diode structure for carrier injection has been realized. The switch is polarization independent and shows an on-off-ratio better than 16.5 dB at a wavelength of 1.3 μm. By time domain measurements the coexistence of the plasma dispersion and the thermo-optical effect is shown. Both effects are separated and quantified.

Avalanche breakdown in (AlxGa1-x)0.52In0.48P pin junctions

The avalanche breakdown behaviour of (AlxGa1-x)0.52In0.48P has been investigated by growing a series of pin diode structures and by measuring the reverse leakage currents until the onset of avalanche breakdown. Comparing the breakdown voltage (Vbd) with that of GaAs, significant increases are obtained, with AlInP having in excess of twice the Vbd of GaAs.

Structural properties of Ga xIn 1−xAs⧸Al yIn 1−y As multiple layers

Multilayer Ga x In 1−xAs/Al y In 1− y As structures grown on InP substrate by molecular beam epitaxy are studied by means of double-crystal X-ray diffraction (DCXD), transmission electron microscopy (TEM), and photoluminescence spectroscopy. The computer simulation of the DCXD curve of the thin modulation-doped single-quantum-well structure ( ∼ 300 nm in total thickness) reveals that it has a very high crystalline perfection. But for a PIN-diode structure of ∼2 μm in total thickness, the DCXD spectrum shows broad peaks. The TEM image of the latter structure reveals many dislocations. The comparison between the thick doped- and undoped-Al y In 1- y As layers suggests that the heavy doping can be one of the causes of the high density of dislocations.

Enhanced breakdown voltages in strained InGaAs/GaAs structures

The breakdown voltage (VBD) in a semiconductor is usually proportional to its band-gap (Eg) through the dependence of the impact ionization process on the threshold voltage (Eth). It has recently been suggested that strain can cause Eth to increase even when Eg decreases, raising the possibility of narrow band-gap materials with large VBD. By growing a range of strained InGaAs/GaAs multiple quantum well (MQW) pin diode structures and measuring VBD, we show that the presence of strained InGaAs increases VBD confirming that it has a larger Eth than GaAs.