The authors have fabricated high-speed, low-threshold 1.3 mu m InGaAsP semi-insulating buried crescent lasers with a CW 3 dB modulation bandwidth of 22 GHz and a threshold current as low as 6.5 mA at room temperature. This is the highest 3 dB modulation bandwidth ever reported for the planar-type semiconductor laser. These results were achieved by implementing a submicron photolithographic process in the channel etching to reduce the cavity width and a polyimide dielectric layer under the bonding pad area to minimize the electrical parasitics.< >

The pulse jitter and bit-error-rate performances of a 1.2 Gbit/s lightwave transmission system using 1.3 mum InGaAsP Fabry-Perot (FP) lasers with Zn-doped active layers were investigated experimentally. It was found that the pulse jitter and the resulting power penalty were strongly dependent on the carrier lifetime of the lasers. This suggests that doped-active FP lasers with decreased carrier lifetime may be usable in a wider range of gigabit lightwave applications than previously considered.

Fe-doped semi-insulating InP layers grown by low-pressure organometallic vapor phase epitaxy with tertiarybutylphosphine have been used as a current block layer for high-speed 1.3-μm InGaAsP buried crescent lasers. The performance characteristics of such lasers are comparable to those of lasers with a PH3-grown Fe-doped semi-insulating InP current blocking layer over a measurement temperature range of 25 to 85 °C. A 3-dB modulation bandwidth of 17.5 GHz has been obtained at room temperature and a cw bias current of 100 mA.

The bit error ratio (BER) performance of a 1.2-Gbit/s lightwave transmission system using 1.3-μm InGaAsP Fabry-Perot (FP) laser diodes with Zn-doped active layers was investigated experimentally. When the laser diodes were tested through a dispersive: fiber, turn-on jitter and mode-partitioning of the lasers contributed to pulse jitter of the optical waveform at the receiver, which in turn led to a dispersion power penalty. It was found that the pulse jitter and the resulting power penalty were strongly dependent on the carrier lifetime of the lasers. Since the doping level of the active layer affects the carrier lifetime, this suggests that doped-active FP laser diodes with a decreased carrier lifetime may be usable in a wider range of gigabit lightwave applications than previously considered.

We report the sucessful fabrication of mesa In0.53Ga0.47As/InP p-i-n photodiodes passivated with SiN(x) films. The SiN(x) films were deposited by plasma-enhanced chemical vapor deposition in two steps. First, a thin SiN(x) film was deposited at low temperature (50-150-degrees-C) and then annealed at high temperature (250-350-degrees-C) for 30-60 min to hydrogenate and nitridize the mesa surfaces simultaneously. Second, a thick SiN(x) film was deposited at the annealing temperature to serve as a surface passivation and antireflective layer. Improvement in dark-current and long-term stability, compared to the results obtained from devices with one-step SiN(x) surface passivation previously reported, has been achieved. The life tests at -20 V and 180/300-degrees-C on these devices have shown a stable dark current for over 1500 h.

Characteristics of Fe-doped semi-insulating (SI) InP layers with overgrown Zn-doped p-type layers have been investigated by scanning electron microscope, secondary-ion mass spectrometry (SIMS), and capacitance-voltage (C-V) and current-voltage (I-V) measurements. Resistivity of the structures determined from the measured I-V characteristics was found to be strongly dependent on the Zn doping concentration. The SIMS depth profiles showed Zn accumulation at the SI/p-InP interface and the peak concentration of the Zn accumulation increased with the doping level and overgrowth time of the p-InP layers. This accumulation of Zn at the SI/p-InP interface correlated with reduction in SI layer resistivity. Accumulation of Zn at the SI/p-InP interface may be minimized by short growth time with low or medium doping of p-InP layers. These growth conditions resulted in high SI layer resistivity. Possible mechanisms for the accumulation of Zn are discussed.

High quality Fe-doped semi-insulating InP epitaxial layers were grown by low-pressure organometallic vapor phase epitaxy using tertiarybutylphosphine (TBP) and triethylindium (TEI) as the reactant sources. Semi-insulating InP epitaxial layers with specular surface morphology and low defect density were obtained at TBP partial pressure higher than 0.38 Torr. Electrical measurements on these layers showed the resistivity of TBP-grown materials to be comparable to that of PH3-grown materials over a measurement temperature range of 25 to 110 °C. A premature reaction between TEI and TBP was observed upstream from the substrate in which things such as TEI:TBP adducts and/or polymers could have been formed. This reaction occurred under low pressure, high gas flow conditions which effectively suppressed analogous reactions for TEI:PH3. As a result, the growth rate of Fe-doped semi-insulating InP layers grown at low pressure with TBP in our reactor decreased by 35% as the V/III ratio was increased from 15 to 46.

The novel concept of K-stabilizing layer is reported for the first time. The coupling coefficient (K) which determines the characteristics of distributed feedback laser diodes (DFB LDs) has been controlled by optimizing the grating depth and layer thicknesses. The coupling coefficient is less dependent on the variations of grating depth and layer thicknesses if an optimized K- stabilizing layer (lower index material like InP) is inserted between the active layer and the guide layer. The controllability of the coupling coefficient has been demonstrated by the standard deviation of the lasing wavelength and the threshold current across a wafer, 0.74 nm and 2.67 mA, respectively.

Fe-doped semi-insulating InP epitaxial layers were grown by low-pressure organometallic vapor phase epitaxy with tertiarybutylphosphine (TBP), triethylindium (TEI) and iron pentacarbonyl [Fe(CO)5] as the reactant gases. The growth was performed by varying the growth rate, growth pressure and V/III ratio. The epitaxial layers were characterized by optical microscopy, secondary ion mass spectrometry, double crystal x-ray diffraction and current-voltage measurements. Semi-insulating InP epitaxial layers with specular surface morphology and low defect density were obtained at TBP partial pressure higher than 0.38 torr. A premature reaction between TEI and TBP was observed which presumably formed TEI:TBP adducts and/or polymers. As a result, the growth rate of Fe-doped semi-insulating InP layers grown at low pressure with TBP in our reactor decreased by 35% as the V/III ratio was increased from 15 to 46. Electrical measurements on these layers showed that the resistivity varied from 1.7×107 to 4×108 Ω cm as the V/III ratio was increased from 15 to 46. The resistivity of TBP-grown materials is comparable to that of PH3-grown materials over a measurement temperature range of 25–110 °C. Selective growth and surface planarization of Fe-doped InP grown with TBP and trimethylindium on patterned etched mesas were achieved.

The dependence of static and dynamic performance on active layer doping concentration in 1.3- mu m InGaAsP semiinsulating buried crescent (SIBC) Fabry-Perot lasers were investigated experimentally. The optical loss in the active region is one of the dominant mechanisms in determining the threshold current for doped active layer lasers. These SIBC lasers have a 3 dB modulation bandwidth of 19 GHz for pulsed operation and 16 GHz for continuous-wave (CW) operation, and a relative intensity noise below -150 dB/Hz for biased current at 120 mA. The doped active lasers show an initial small degradation rate at 65 degrees C operation, which gives an acceptably long operation lifetime. >

A novel U-groove distributed feedback (U-DFB) laser structure is reported for the first time. This new U-DFB laser shows threshold current of 34 mA, external total quantum efficiency of 0.4 mW/mA from both facets and side mode suppression ratio of 30 dB.

We have investigated, experimentally, the coherent operation of 1-dimensional linear arrays of grating coupled surface emitting lasers for different laser designs (gain lengths, grating parameters). For laser arrays with shailow grating teeth and strong inter-element coupling a diffraction limited far field of 0.012 degrees full width half maximum was obtained from up to 6 coupled lasers extending over a length of 3.5mm.

A review of high frequency InGaAsP/InP laser structures is presented. The performance of these devices is analyzed based on a rate equations model. The effects of packaging and device parasitics on high speed modulation are also considered through a circuit configuration. The model is used to compare the relative advantages of the main high frequency laser structures in order to maximize the obtainable modulation bandwidth. The characteristics of buried crescent lasers with semi-insulating current-blocking layers are highlighted. A 3-dB direct modulation bandwidth of 11 GHz together with 42-mW output power has been achieved with this device.

A high-speed and high-power InGaAsP semi-insulating buried crescent (SIBC) laser operating at 1.3-μm wavelength is described. The laser is fabricated with two epitaxial growth steps. A 3-dB direct modulation bandwidth of 11 GHz and a maximum cw output power of 42 mW have been achieved. A model based on rate equations is used to analyze these laser diodes. The effects of packaging and device parasitics on high-speed modulation are incorporated through a simple circuit configuration. The calculated frequency response is in good agreement with the measured response. The model is then used to predict the maximum obtainable modulation bandwidth. Finally, the measured relative intensity noise performance of the SIBC laser is presented.

Cobalt-doped semi-insulating InP layers grown by low-pressure metalorganic chemical vapor deposition (LPMOCVD) have been used for the first time as a current blocking layer for 1.3 μm InGaAsP buried crescent lasers. Lasers with this cobalt-doped InP blocking layer have cw threshold currents as low as 8 mA at room temperature. This is the lowest cw threshold current yet reported for an InGaAsP laser with a semi-insulating current blocking layer. In addition, the lasers exhibit total differential quantum efficiency of 60%, high-temperature operation up to 100 °C, high output power of 30 mW/facet, and a 3-dB modulation bandwidth of 11.6 GHz. These results indicate that the cobalt-doped semi-insulating InP layer grown by LPMOCVD provides effective current blocking for high-performance lasers.

The dependence of current-voltage (I-V) characteristics on Fe-doped semi-insulating (SI) InP layer thickness has been investigated experimentally. The I-V characteristics exhibit nonlinear behavior with ohmic, transition, and space-charge-limited regimes. An approximate circuit model of the buried crescent laser which describes the dynamic characteristics of the SI current blocking layers is presented. It is shown that for a 5-μm-thick SI layer, a very high resistivity of 4.9×108 Ω cm and a very low capacitance of 1 pF are obtained at the typical operating voltage for laser diodes of 1–2 V. Thus, semiconductor lasers with Fe-doped SI InP current blocking layers offer great promise for achieving both wide modulation bandwidth and high-power operation.

A semiconductor laser wherein a wide range of laser emission wavelengths can be obtained by varying the composition of monocrystalline alloys employed as semiconductor material. The semiconductor structure comprises on a monocrystalline indium phosphide substrate of a predetermined conductivity type successive epitaxial layers consisting of a first confinement layer of the same conductivity type, an active layer having the formula (Gax Al1-x)0.47 In0.53 As where x is within the range of 0 to 0.27, and a second confinement layer of opposite conductivity type. The confinement layers are composed of either InP or a ternary alloy Al0.47 In0.53 As or a quaternary alloy Gax' Al1-x' Asy' Sb1-y' where x' and y' are chosen so that the material should have a predetermined crystal lattice and an energy gap of greater width than the substrate material.

The fabrication and performance of high-speed and high-power 1.3-μm InGaAsP buried crescent lasers with semi-insulating current blocking layers are reported. A modulation bandwidth of 11 GHz and acw output power of 42 mW/facet have been achieved. An approximate circuit model of the semi-insulating buried crescent laser, which describes the effect of dc bias on parasitic capacitance at high-speed operation, is also presented.

A hybrid growth technique has been used to fabricate low threshold 1.51 and 1.3 µm InGaAsP buried crescent (BC) injection lasers with a semi-insulating current confinement layer. The technique involves a first stage of low pressure metal organic chemical vapor deposition (LPMOCVD) followed by a liquid phase epitaxy (LPE) stage. The BC lasers exhibit CW threshold currents as low as 12 mA at 25'C, high yield, differential quantum efficiency over 41%, and output power more than 18 mW. Small-signal modulation response to 3.5 GHz and 5 GHz has been obtained for 1.51 and 1.3 um laser respectively. The BC lasers show an initial small degradation rate of 1%/kh at 50'C which gives an estimated operating lifetime of 47 years at 25'C.