Improved frequency response of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading and multiplication regions

We report very high-speed operation of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading and multiplication regions (SAGM-APDs). For low multiplication values (M0?7) the bandwidth of these APDs is relatively insensitive to the gain and is determined by the hole transit time and the RC time constant. In this gain region bandwidths as high as 5.5 GHz have been achieved. For higher multiplication values the frequency response exhibits a constant gain-bandwidth product. We have observed gain-bandwidth products as high as 40 GHz, the highest value reported to date for a device of this type.     

Avalanche buildup time of InP/InGaAsP/InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions

The avalanche buildup time of an avalanche photodiode can be determined from the frequency response of the noise power as a function of the dc multiplication M0. In this paper we report on the first measurements of the avalanche buildup time of InP/InGaAsP/ InGaAs avalanche photodiodes with separate absorption, grading, and multiplication regions (SAGM-APD's). Measurements on several different device structures reveal that the avalanche buildup time (gain-bandwidth product) decreases (increases) with increasing carrier concentration in the multiplication region. The shortest buildup time that we have observed wasM_{0} times 4.2ps which corresponds to a gain-bandwidth Product of 38 GHz.     

Multiplication noise of wide-bandwidth InP/InGaAsP/InGaAs avalanchephotodiodes

Measurements of InP/InGaAsP/InGaAs separate absorption, grading, and multiplication avalanche photodiode multiplication indicate that at high gains the excess noise factors approach values predicted by the conventional continuum theory. However, at lower gains the noise is suppressed. This is probably an artifact of the very thin multiplication layers which have been used to increase the gain-bandwidth product. From the frequency response of the noise power, a gain-bandwidth product of 60 GHz, which is consistent with the value of 57 GHz obtained directly from bandwidth measurements, is deduced     

InGaAs/InAlAs雪崩光电二极管仿真设计

设计了一种InGaAs/InALAs雪崩光电二极管(APD),并利用MEDICI软件进行了模拟仿真.器件采用背入射探测方式.雪崩增益区采用埋层设汁,省略了保护环等结构;并使用双层掺杂,有效降低了增益区电场的梯度变化.由于结构简单,因此仪需要利用分子束外延(MBE)生长精确控制每层结构即可.由于InAlAs材料的空穴与电子的离化率有较大的筹异,因此器件具有较低的噪声因子.     

InAlAs/InGaAs HBT X-band double-balanced upconverter

We report on an InAlAs/InGaAs HBT Gilbert cell double-balanced mixer which upconverts a 3 GHz IF signal to an RF frequency of 5-12 GHz. The mixer cell achieves a conversion loss of between 0.8 dB and 2.6 dB from 5 to 12 GHz. The LO-RF and IF-RF isolations are better than 30 dB at an LO drive of +5 dBm across the RF band. A pre-distortion circuit is used to increase the linear input power range of the LO port to above +5 dBm. Discrete amplifiers designed for the IF and RF frequency ports make up the complete upconverter architecture which achieves a conversion gain of 40 dB for an RF output bandwidth of 10 GHz. The upconverter chip set fabricated with InAlAs/InGaAs HBT's demonstrates the widest gain-bandwidth performance of a Gilbert cell based upconverter compared to previous GaAs and InP HBT or Si-bipolar IC's     

A New Planar InGaAs–InAlAs Avalanche Photodiode

We discuss a new simple InGaAs–InAlAs avalanche photodiode (APD) with a planar buried multiplication region. Some of the advantages compared to standard APDs are as follows: 1) The thickness of the avalanche and the charge control regions are accurately controlled by molecular beam epitaxy growth in contrast to the standard diffusion process; 2) InAlAs is the multiplication material (avalanching faster electrons) instead of InP (avalanching slower holes); 3) InAlAs avalanche gain has a lower noise figure than that for InP; 4) a guard ring is not required; 5) fabrication is as simple as that for a p-i-n detector; 6)the APD has high wafer uniformity, and high reproducibility; 7)the InAlAs breakdown voltage is lower than InP, and its variation with temperature is three times lower than that for InP; 8) excellent aging and reliability including Telcordia GR-468 qualification for die and modules; 9) high gain-bandwidth product as high as 150 GHz; and 10) high long-range (LR-2) bit-error-rate$10^-12$receiver sensitivity of$-$29.0 dBm at 10 Gb/s,$-$28.1 at 10.7Gb/s, and$-$27.1 dBm at 12.5 Gb/s.     

Optimization of charge and multiplication layers of 20-Gbps InGaAs/InAlAs avalanche photodiode

We calculated the correlation between the doping concentration of the charge layer and the multiplication layer for separate absorption, grading, charge, and multiplication InGaAs/InAlAs avalanche photodiodes (APDs). For this purpose, a predictable program was developed according to the concentration and thickness of the charge layer and the multiplication layer. We also optimized the design, fabrication, and characteristics of an APD for 20 Gbps application. The punch-through voltage and breakdown voltage of the fabricated device were 10 V and 33 V, respectively, and it was confirmed that these almost matched the designed values. The 3-dB bandwidth of the APD was 10.4 GHz, and the bit rate was approximately 20.8 Gbps.     

Planar InP-InGaAs avalanche photodetectors with n-multiplicationlayer exhibiting a very high gain-bandwidth product

A planar separate absorption, grading, charge, and multiplication (SAGCM) avalanche photodiode (APD) structure was designed and fabricated, allowing for an updoped multiplication layer without the use of guard rings. A very high gain-bandwidth (GBW) product of 93 GHz and DC gains exceeding 1000 have been measured for a 30-μm-diameter device. This GBW is, to the author's knowledge, the highest reported to date in any III-V APD. In principle, the useful gain-bandwidth product of SAGCM structures is not limited by the tunneling limit in the InP avalanche region of 140 GHz for conventional separate absorption, grading, and multiplication (SAGM) structures     

Wideband DHBTs using a graded carbon-doped InGaAs base

We report an InP/InGaAs/InP double heterojunction bipolar transistor (DHBT), fabricated using a mesa structure, exhibiting 282 GHz f/sub /spl tau// and 400 GHz f/sub max/. The DHBT employs a 30 nm InGaAs base with carbon doping graded from 8/spl middot/10/sup 19//cm/sup 3/ to 5/spl middot/10/sup 19//cm/sup 3/, an InP collector, and an InGaAs/InAlAs base-collector superlattice grade, with a total 217 nm collector depletion layer thickness. The low base sheet (580 /spl Omega/) and contact (<10 /spl Omega/-/spl mu/m/sup 2/) resistivities are in part responsible for the high f/sub max/ observed.     

Double junction AlInAs/GaInAs multiquantum well avalanche photodiodes

A separate absorption, grading, and multiplication avalanche photodiode with an AlInAs/GaInAs multiquantum well multiplication region is reported. This device exhibits a low excess-noise factor and a gain-bandwidth product of 50 GHz, due to the high ratio of ionisation rates of the multiplication material. In addition, a large bandwidth is obtained owing to the use of an undoped (n type) GaInAs absorption layer, fully depleted when multiplication occurs.<>     

High-performance In0.52Al0.48As/In0.53Ga0.47As HFET compatible with optical-detectorintegration

The authors report the successful demonstration of a 1.0-μm gate InAlAs/InGaAs heterojunction FET (HFET) on top of thick InGaAs layers using lattice-matched molecular beam epitaxy (MBE). This scheme is compatible with metal-semiconductor-metal (MSM) photodetector fabrication. The authors measured the performance of InAlAs/InGaAs HFETs from 0 to 40 GHz. Device performance is characterized by peak extrinsic transconductances of 390 mS/mm and as-measured cutoff frequencies up to 30 GHz for a nominal 1.0-μm-gate-length HFET. HFET device measurements are compared for samples growth with and without the thick underlying InGaAs optical-detector absorbing layer     

InGaAs/InAlAs multiquantum-well waveguided pin photodiodes withwide tunability and avalanche multiplication

A new high-speed, waveguided InP based on the InGaAs/InAlAs multiquantum-well pin photodiode with gain and fabricated by metal organic vapour phase epitaxy is reported. The quantum-confined Stark effect can be used to tune this diode over a 250 nm range in the wavelength region around 1.55 μm. A 3 dB bandwidth of more than 12 GHz and avalanche multiplication have been observed     

Disordering by Zn-diffusion of InGaAs/InAlAs MQW superlattice structure grown by MBE

Disordering of MBE-grown InGaAs/InAlAs MQW (multiquantum well) superlattice structures by Zn-diffusion was studied for the first time. Optical measurements and sputtering Auger electron measurements revealed that the InGaAs/InAlAs MQW superlattice structure is easily disodered by Zn-diffusion. On the other hand, the MQW superlattice structure is stable against the thermal treatment up to 700°C.     

Noise properties and time response of the staircase avalanche photodiode

The staircase avalanche photodiode is a novel graded-gap superlattice device that is expected to detect photons quite noiselessly. It is designed in such a way that only electrons impact-ionize, thereby eliminating the feedback noise associated with conventional two-carrier avalanche devices. Because the electron multiplication can occur only at a small number of discrete locations in the device, the variability of the number of electrons generated per detected photon is minimized. The excess noise and the electron counting distribution are obtained as a function of the number of stages in the device and the impact-ionization probability per stage, for instantaneous multiplication. The (single-photon) impulse response function is calculated when the effects of (random) transit time are incorporated into the carrier multiplication process. Inclusion of the time dynamics is essential for determining the time course of the current generated by the device in response to pulses of light. This, in turn, permits bit error rates to be calculated for systems incorporating the device. For a five-stage quaternary device the gain-bandwidth product is calculated to be in the vicinity of 600 GHz.     

Noise properties and time response of the staircase avalanche photodiode

The staircase avalanche photodiode is a novel graded-gap superlattice device that is expected to detect photons quite noiselessly. It is designed in such a way that only electrons impact-ionize, thereby eliminating the feedback noise associated with conventional two-carrier avalanche devices. Because the electron multiplication can occur only at a small number of discrete locations in the device, the variability of the number of electrons generated per detected photon is minimized. The excess noise and the electron counting distribution are obtained as a function of the number of stages in the device and the impact-ionization probability per stage, for instantaneous multiplication. The (single-photon) impulse response function is calculated when the effects of (random) transit time are incorporated into the carrier multiplication process. Inclusion of the time dynamics is essential for determining the time course of the current generated by the device in response to pulses of light. This, in turn, permits bit error rates to be calculated for systems incorporating the device. For a five-stage quaternary device the gain-bandwidth product is calculated to be in the vicinity of 600 GHz.     

Performance of thin separate absorption, charge, and multiplicationavalanche photodiodes

Previously, it has been demonstrated that resonant-cavity-enhanced separate-absorption-and-multiplication (SAM) avalanche photodiodes (APDs) can achieve high bandwidths and high gain-bandwidth products while maintaining good quantum efficiency. In this paper, we describe a GaAs-based resonant-cavity-enhanced SAM APD that utilizes a thin charge layer for improved control of the electric field profile. These devices have shown RC-limited bandwidths above 30 GHz at low gains and gain-bandwidth products as high as 290 GHz. In order to gain insight into the performance of these APDs, homojunction APDs with thin multiplication regions were studied. It was found that the gain and noise have a dependence on the width of the multiplication region that is not predicted by conventional models. Calculations using width-dependent ionization coefficients provide good fits to the measured results. These calculations indicate that the gain-bandwidth product depends strongly on the charge layer doping and on the multiplication layer thickness and, further, that even higher gain-bandwidth products can be achieved with optimized structures     

InAlAs/InGaAs heterostructure FET's processed with selectivereactive-ion-etching gate-recess technology

A highly selective reactive-ion-etching process based on HBr plasma has been used as a gate-recess technique in fabrication of InAlAs/InGaAs heterostructure FETs. A typical 0.75-μm-gate-length transistor exhibited a threshold voltage of -1.0 V, a maximum extrinsic transconductance of 600 mS/mm, an extrinsic current-gain cutoff frequency of 37 GHz, and a maximum frequency of oscillation of 90 GHz. These DC and RF device parameters compare favorably with those of a corresponding device gate-recessed with a selective wet-etching technique     

Characteristics of InAlAs/InGaAs high-electron-mobility transistorsunder illumination with modulated light

The optical response of InAlAs/InGaAs HEMT's under illumination with modulated light from a 1.3-μm semiconductor laser diode onto the backside of the substrate is measured by using an optical-signal analyzer. It is clear that the response is composed of two signals. One signal is dominant at a low frequency and is due to the photovoltaic effect that causes excess holes photogenerated in the InGaAs channel to accumulate in the source region. This accumulation thus causes a decrease in the threshold voltage of the HEMTs. To explain this mechanism, a theory is given which connects the change in threshold voltage with that in the Fermi energy of the two-dimensional electron gas (2-DEG). The other signal is dominant at a high-frequency and is due to the photoconductive effect in the InGaAs channel beneath the gate. In this case, a large optical gain is produced since electrons at the source region are replenished in the gate channel. This leads to the first clear observation of a photoconductive signal. The bandwidth due to the photovoltaic effect is as low as 45 MHz and is dominated by the lifetime of the excess holes. The bandwidth due to the photoconductive effect is as high as 37 GHz and is dominated by the gain-bandwidth product of transistors rather than the intrinsic transit-time of electrons     

5 V, DC-12 GHz InP/InGaAs HBT amplifier

An InP/InGaAs HBT cascode amplifier operating from a single 5 V power supply is described. The circuit has a DC gain of 17.2 dB and a -3 dB frequency point of 12.3 GHz. This results in a gain-bandwidth product in excess of 90 GHz. The frequency response of the amplifier remains constant if the power supply voltage is as low as 4 V.<>     

A wide-bandwidth low-noise InGaAsP-InAlAs superlattice avalanchephotodiode with a flip-chip structure for wavelengths of 1.3 and 1.55μm

The authors reports the fabrication of a flip-chip InGaAsP-InAlAs superlattice avalanche photodiode using gas source molecular beam epitaxy. The incident light reaches the InGaAs photoabsorption layer through the InP substrate and an InGaAsP-InAlAs superlattice multiplication region which are transparent for wavelengths of 1.55 and 1.3 μm. The light reflection by the electrode enables the absorption layer to be as thin as 0.8 μm without significantly reducing the quantum efficiency. A maximum bandwidth of 17 GHz was obtained at a low multiplication factor because the transit time through the absorption layer is reduced