S. G. Napholtz

Pt/Ti/p‐In0.53Ga0.47As low‐resistance nonalloyed ohmic contact formed by rapid thermal processing

Very low resistance nonalloyed ohmic contacts of Pt/Ti to 1.5×1019 cm−3 Zn‐doped In0.53Ga0.47As have been formed by rapid thermal processing. These contacts were ohmic as deposited with a specific contact resistance value of 3.0×10−4 Ω cm2. Cross‐sectional transmission electron microscopy showed a very limited interfacial reacted layer (20 nm thick) between the Ti and the InGaAs as a result of heating at 450 °C for 30 s. The interfacial layer contained mostly InAs and a small portion of other five binary phases. Heating at 500 °C or higher temperatures resulted in an extensive interaction and degradation of the contact. The contact formed at 450 °C, 30 s exhibited tensile stress of 5.6×109 dyne cm−2 at the Ti/Pt bilayer, but the metal adhesion remained strong. Rapid thermal processing at 450 °C for 30 s decreased the specific contact resistance to a minimum with an extremely low value of 3.4×10−8 Ω cm2 (0.08 Ω mm), which is very close to the theoretical prediction.

Pt/Ti Ohmic contact to p++‐InGaAsP (1.3 μm) formed by rapid thermal processing

Nonalloyed Ohmic contacts of evaporated Pt/Ti to p‐InGaAsP (λg=1.3 μm) with different Zn doping levels ranging 5×1018–2×1019 cm−3 have been fabricated by rapid thermal processing. These contacts showed Ohmic behavior prior to any heat treatment with a specific contact resistance of 4×10−3 Ω cm2 for the lowest doping level and 1×10−4 Ω cm2 for the highest level. A decrease in the specific resistance was achieved by supplying rapid thermal processing to the contacts, while the lowest values were observed on all the contacts as a result of heating at 450 °C for 30 sec. The lowest resistance of 1×10−6 Ω cm2 was achieved at the contact that was formed on the 2×1019 cm−3 Zn‐doped InGaAsP layer. Measurements of the conduction activation energy yields a good linear dependence of the specific resistance on temperature in all the contacts as deposited and after the different heat treatments. The higher the doping level and the rapid thermal processing temperature up to 450 °C, the lower the activation energy, which...

InGaAsP laser with semi‐insulating current confining layers

The fabrication and performance characteristics of a InGaAsP laser structure with semi‐insulating current confining layers are reported. The semi‐insulating layers are Fe‐doped InP and are grown using the metalorganic chemical vapor deposition growth technique. The lasers have threshold currents in the range 20–30 mA and external differential quantum efficiency ∼0.2 mW/mA/facet at 30 °C. The bandwidth for small‐signal response is ∼2 GHz which suggests that the laser structure is suitable for high bit rate lightwave transmission systems. Initial aging results yield an estimated operating lifetime of 10 years at 20 °C.

Long wavelength InGaAsP (λ∼1.3 μm) modified multiquantum well laser

The fabrication and performance characteristics of InGaAsP (λ∼1.3 μm) double channel planar buried heterostructure lasers with multiquantum well (MQW) active layers are reported. The MQW structure has λg∼1.3 μm InGaAsP active wells and λg∼1.03‐μm InGaAsP barrier layers. The lasers have threshold current of ∼20 mA at 30 °C and external differential quantum efficiencies of ∼0.2 mW/mA/facet at 30 °C. The temperature dependence of threshold current is characterized by T0∼100 K both under electrical and optical pumping. The lasers have been operated to 110 °C and up to ∼30 mW/facet at 25 °C. The measured dynamic linewidth under modulation is ∼2 smaller than that for conventional double heterostructure lasers. The lower temperature dependence of threshold current and smaller dynamic linewidth makes real index‐guided InGaAsP MQW active layer lasers potentially attractive for many system applications.

InGaAsP distributed feedback multiquantum well laser

The fabrication and performance characteristics of 1.3 μm InGaAsP distributed feedback (DFB) lasers with multiquantum well (MQW) active layers are reported. The lasers are of the double channel planar buried heterostructure type and utilize a second order grating with a periodicity of ∼3900 A for frequency selective feedback. The lasers have threshold currents in the range 25–35 mA at 30 °C and external differential quantum efficiencies of 0.2 mW/mA/facet at 30 °C. The temperature dependence of threshold current is characterized by a T0 value of 95–100 K. The lasers have been operated to an output power of 19 mW in a single frequency. The measured dynamic linewidth under modulation is a factor of 2 smaller than that for regular double heterostructure lasers. The lower temperature dependence of threshold current and smaller dynamic linewidth make real index guided InGaAsP DFB MQW active layer lasers attractive for many system applications.

Fabrication and performance characteristics of InGaAsP multiquantum well double channel planar buried heterostructure lasers

We report the fabrication and performance characteristics of InGaAsP double channel planar buried heterostructure (DCPBH) lasers with multiquantum well active layers emitting at 1.3 μm. These lasers have threshold currents in the range 40–50 mA at 30 °C, external differential quantum efficiencies of ∼50% at 30 °C, and T0 values ∼160–180 K in the temperature range 10–60 °C. Under optical pumping the measured T0 are in the range 100–150 K. The lasers operate in a single transverse mode up to high powers (>10 mW/facet), can be modulated at ∼2 Gb/s, and exhibit less frequency chirping than similar lasers with conventional active layers. The observed high T0 and smaller chirp make DCPBH multiquantum well lasers potentially attractive for system applications.

1.5‐μm GaInAsP planar buried heterostructure lasers grown using chemical‐beam‐epitaxial base structures

GaInAsP/InP double heterostructures grown by chemical‐beam epitaxy have been used in conjunction with liquid‐phase‐epitaxial regrowth to fabricate high‐performance buried heterostructure lasers operating at a wavelength of 1.5 μm. These lasers show room‐temperature threshold currents as low as 12 mA, external quantum efficiencies as high as 0.2 mW/mA per facet, and, in general, linear output power up to ∼10 mW/facet. The 3‐dB bandwidth at optimal biasing is about 8 GHz and is believed to be limited by the heatsink stud. The relative intensity noise is low, <−150 dB/Hz at 1 GHz for bias currents from 50 mA to above 150 mA.

High‐power gain‐guided InGaAsP laser array

We have fabricated InGaAsP gain‐guided laser arrays emitting at 1.3 μm. These devices have threshold currents in the range 300–400 mA at 30 °C and have been operated to pulsed output powers as high as 400 mW. More than 100 mW of output power has been obtained up to an ambient temperature of 60 °C. The lasers emit in multilongitudinal modes with a far‐field divergence of 20°×35°. A gain‐guided InGaAsP laser array of the type described here can be used in some applications requiring high‐power lasers emitting at 1.3 μm.

InGaAsP ridge waveguide laser array with nonuniform spacing

The fabrication and performance characteristics of InGaAsP (λ∼1.3 μm) ridge waveguide laser arrays are described. The ridges have variable spacing but are chosen to be of equal widths so that the propagation constants, which determine the emission wavelengths, of the individual emitters are equal. The lasers have threshold currents in the range 300–350 mA at 30 °C and have been operated to pulsed output powers of 600 mW/facet. The far field along the junction plane is single lobed with a width characteristic of a phase locked, diffraction limited beam. Measurements of cw emission spectrum also show emission in a single fundamental supermode.

High‐power operation of InP/InGaAsP double‐channel planar buried‐heterostructure lasers with asymmetric facet coatings

We report the high‐power operation of λ=1.3 μm InGaAsP double‐channel planar buried‐heterostructure lasers with asymmetric mirror coatings. A stack of four dielectric layers is used to raise the reflectivity of one facet to over 80%, and the thickness of a single layer coating on the output facet is chosen to reduce the reflectivity to about 4%. The resulting lasers are characterized by a low threshold current of 25 mA, slope efficiency as high as 50%, and a power output of as much as 150 mW (at 5 °C) at a current of less than 300 mA. The lasers operate in a single transverse mode over the entire current range and as much as 45 mW of power could be coupled into a lensed single‐mode fiber. Preliminary high‐power aging data show excellent device reliability.