Te-Chin Peng

10-Gb/s InGaAs p-i-n Photodiodes With Wide Spectral Range and Enhanced Visible Spectral Response

By selectively removing the InP cap layer on top of the conventional double-heterojunction InP-InGaAs-InP p-i-n photodiodes (PDs), a PD with high quantum efficiency in the 0.55- to 1.65-mum spectral range was realized. With antireflection coating designed both for 0.85- and 1.3-mum wavelengths, quantum efficiency higher than 80% in the 0.85- to 1.65-mum range and higher than 70% in the 0.55- to 1.65-mum range was achieved. In addition, we use a novel chip-level package technique, a self-positioned micro-ball-lens on chip, to get a large spatial alignment tolerance for the PDs. The combination of these two features significantly enhances the spectral and spatial detection range of our 10-Gb/s InGaAs p-i-n PD. Besides, exhibiting a dark current smaller than 50 pA, the PD has a 3-dB bandwidth higher than 10.3 GHz at 1.3-mum wavelength. At the 10.3-Gb/s data rate, back-to-back eye diagrams of the PD are both wide open at 0.85- and 1.3-mum wavelengths. Since both high-efficiency and high-speed operation can be achieved, receivers based on such devices are suitable for both 0.85- and 1.3-mum single-mode and multimode fiber-optic communication systems

Temperature Dependent Photoluminescence of Self-Organized InAs Quantum Dots on an InGaAs Strain Buffer Layer Grown by MOCVD

In this article, we investigate the formation and optical properties of 3-monolayer (ML) InAs quantum dots (QDs) on the InGaAs strain buffer layer (SBL) grown by metallorganic chemical vapor deposition (MOCVD). As compared to the InAs QDs directly grown on a GaAs surface, the InAs QDs grown on an InGaAs SBL can increase the dot density from 1.7 to 3.5 X 10 10 cm -2 and improve the uniformity. Using microphotoluminescence (μ-PL) measurements, the power-dependent PL at low temperatures shows the ground, first, and second states of InAs QDs due to the state-filling effect at the highest excitation power density of 11900 W/cm 2 . The temperature-dependent PL spectra shows that the PL peak energy has a redshift following the Varshni relation and an unusual temperature dependence of the linewidth, which first reduces and then increases with temperature for the InAs QDs grown on the InGaAs SBL. The PL thermal quenching is determined by the carrier escape from the QDs to the nonradiative recombination centers. The peak wavelength and full width at half maximum of PL spectra at 280 K for the InAs QDs grown on an InGaAs SBL are 1306 nm and 21.5 meV, respectively.

High-speed and uncooled operation of 1.3-/spl mu/m InGaAsP strain-compensated MQW BH lasers fabricated on patterned InP substrates

The fabrication and characteristics of 1.3-/spl mu/m InGaAsP strain-compensated multiquantum well (SCMQW) buried heterostructure (BH) laser diodes (LDs) grown by selective metal-organic chemical vapor epitaxy on a patterned InP substrate are demonstrated. The photoluminescence (PL) of the SCMQW active region grown on the patterned grooves has a narrow full-width at half-maximum of /spl sim/ 47 meV. The BH LDs exhibit a threshold current of 6.8 mA, a slope efficiency of 0.45 mW/mA, and a light output power exceeding 30 mW at 80 mA and 20/spl deg/C. The maximum operating temperature is 120/spl deg/C with a characteristic temperature of 72 K in 20/spl deg/C-80/spl deg/C. The 3-dB modulation bandwidth can be extended as far as 11.4 GHz under a bias level of 40 mA, and the back-to-back tests show a clear and symmetric eye diagram at 10 Gb/s with a PRBS of 2/sup 31/-1 word length and a peak-to-peak voltage of 1.08 V at 85/spl deg/C. The average increase in operational current is smaller than 0.84% after the 1500-h aging test. The mean time of the BH LDs operated at 85/spl deg/C to fail is calculated as 9/spl times/10/sup 4/ h. These BH LDs satisfy the reliability requirement for strict loop environment and 10-Gb Ethernet application without special hermetic packaging.

Low-cost and high-performance 1.3-/spl mu/m AlGaInAs-InP uncooled laser diodes

In this letter, we utilize a self-terminated oxide polish (STOP) planarization technique to fabricate high-yield, high-performance, low-cost, and uncooled 1.3-mum ridge-waveguide AlGaInAs-InP laser diodes (LDs). The STOP technique is superior to the polyimide planarization, which suffers from high-temperature sustainability. The LDs fabricated by the STOP technique exhibit threshold currents of 8.5 and 30.5 mA, and light output powers of 25.9 and 4.8 mW at 100 mA for 20degC and 110degC, respectively. The characteristic temperatures (T 0) are 82.6 K from -30degC to 80degC and 55.9 K from 80degC to 110degC. Since the metal pad lies on a thick SiO2 layer, the parasitic capacitance can be effectively lowered to 2 pF. The 3-dB modulation bandwidths of the LDs at 50 mA are 12.1 and 9.44 GHz at 20degC and 90degC, respectively

Alignment tolerance enlargement of a high-speed photodiode by a self-positioned microball lens

By integrating a commercially available microball lens on the InGaAs p-i-n photodiode chip, we have achieved at least 5- and 16-fold improvements of the optical alignment tolerance in the transverse and longitudinal axes, respectively, without sacrificing the diode efficiency. The optical alignment during lens/chip integration is achieved by a self-positioning process, which provides an on-chip ball-lens socket in concentric circles to the photodiode aperture to sustain the drop-in microball lens. The photodiode after lens integration exhibits a 3-dB bandwidth larger than 9 GHz and a responsivity larger than 0.9 A/W, both at 1310-nm wavelength. In addition, the InGaAs photodiode exhibits a dark current density of less than 3 /spl mu/A/cm/sup 2/, both before and after lens positioning, indicating a proper integration.

Self-terminated oxide polish technique for the waveguide ridge laser diode fabrication

Semiconductor lasers fabricated by the traditional process for communication application usually adopt a ridge-waveguide structure for its ease of manufacture. However, the rugged planes of these devices would cause metal coverage problems and interconnection difficulty. A planarization technique based on a self-aligned technique for fabricating the ridge-weaveguide semiconductor laser diode is introduced in this article. The technique is based on a process called “self-terminated oxide polish.” By using this technique, metal coverage problems usually encountered in the laser diode with a double trench structure will be reduced. Since the metal pad lies on a thick oxide layer, the device will also have a lower parasitic capacitance, which will be beneficial to high-speed operation. Device characteristics of several ridge-waveguide laser diodes fabricated using this self-aligned method will be presented.

Monte Carlo ray trace simulation for micro-ball-lens-integrated high-speed InGaAs p-i-n photodiodes

To widen the alignment tolerance of a 10Gbytes∕s InGaAs p-i-n photodiode, which typically only has an optical coupling aperture of 30μm in diameter, we have developed a self-positioning ball-lens-on-chip scheme for enlarging the effective coupling aperture. According to the measured results, the 4.5- and 5.3-fold improvements along the transverse and optical axes, respectively, in alignment tolerance have been demonstrated without sacrificing the diode efficiency as a commercially available ruby micro-ball-lens (MBL) with a 300μm lens diameter integrated on the high-speed photodiode. To further explore the aperture enlargement capability and optimize the structural design, we have constructed a ray trace model based on the Monte Carlo method for the optical coupling system as well. Using this well-constructed simulation model, we further predict that, by integrating a 250μm diametric ruby MBL on the photodiode with a 20μm high lens socket, the alignment tolerance can have 7.1- and 10-fold improvements alo...

A simple and low-cost fabrication of polymeric vertical microlens using dip method

Polymeric vertical microlenses (PVMs) using photoresist material SU-8 are fabricated with a simple and low-cost process that can be easily applied to the microoptical/optoelectronic bench. By virtue of the strong adhesive force and liquid cohesion, the PVMs are formed by hanging the liquid SU-8 on walls by a dip method. Then, in order to enhance the thermal stability and reliability of the PVMs, the lenses are baked and exposed in the ultraviolet light to crosslink the SU-8. To characterize the PVMs, we use a single-mode fiber carrying a 1.55-/spl mu/m wavelength laser light source and utilize BeamScope P5 to observe the beam convergences. The output beams through the PVMs show a vertical far-field angle of 3.04/spl deg/, as compared to 5.53/spl deg/ of the beam without passing through the lenses.

High-Temperature and High-Frequency Operation of 1.3 μm AlGaInAs ∕ InP Laser Diodes Using Silicon Oxide Planarization

In this article, a self-terminated oxide polish (STOP) planarization technique is utilized to fabricate high-temperature and highspeed 1.3 μm AlGaInAs/InP ridge-waveguide laser diodes (LDs). The as-cleaved LDs fabricated by this STOP technique exhibit a threshold current of 8.5 and 57.5 mA, and a light output power of 27 and 2.4 mW at 100 mA for 0 and 130°C, respectively. The characteristic temperature (To) is 85.5 K from 0 to 80°C and 54.1 K from 80 to 130°C. The full width at half maximum of the lateral far-field angle is 34° for the conventional ridge LDs and reduces to 22° for the LDs by the STOP technique. The 3 dB modulation bandwidth at 100 mA of the LDs can reach 16.9 at 20°C and 10.9 GHz at 90°C.

1.32 μm InAs/GaAs quantum-dot resonant-cavity light-emitting diodes grown by metalorganic chemical vapor deposition

The first demonstration of InAs∕GaAs quantum-dot (QD) resonant-cavity light-emitting diode (RCLED) operating at 1.32μm at room temperature is reported. A single-layer InAs QDs inserted in GaAs matrix as the active medium was grown by metalorganic chemical vapor deposition. The bottom and top mirrors of QD RCLEDs were fabricated by employing epitaxial AlGaAs∕GaAs pairs and one dielectric SiO2∕Si3N4 pair as distributed Bragg reflectors (DBRs), respectively. As compared to the nonresonant QD LEDs, the RCLEDs exhibit a forward voltage of 1.13V at 20mA, a peak wavelength of 1.318μm, a narrower full width at half maximum in the electroluminescent spectrum of 14meV at 20mA, a high Q factor of 73.9, a low redshift rate with injection current of 0.033nm∕mA, and a higher light-output power of 28μW at 100mA.