Ami Appelbaum

Growth and characterization of Fe‐doped semi‐insulating InP prepared by low‐pressure organometallic vapor phase epitaxy with tertiarybutylphosphine

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.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 th...

High quality Fe‐doped semi‐insulating InP epitaxial layers grown by low‐pressure organometallic vapor phase epitaxy using tertiarybutylphosphine

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.

Effect of zinc diffusion from overgrown p-InP layers on semi-insulating InP

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.

1.3 μm InGaAsP buried crescent lasers with cobalt‐doped semi‐insulating current blocking layers grown by metalorganic chemical vapor deposition

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.

Reduction of specific contact resistance on GaInAsP by rapid thermal process anneal

An order of magnitude improvement in the specific contact resistance of gold‐based ohmic contacts to p‐type GaInAsP (Eg=1.13 eV) is reported. A novel technique using a silicon susceptor has been employed in a rapid thermal processor. A direct comparison between gold‐based contacts annealed in a conventional furnace and the rapid thermal processor indicated a specific contact resistance of 4.2×10−5 and 4.1×10−6 Ω cm2, respectively. Auger electron spectroscopy, in depth profile mode, revealed two different metallurgical profiles for the conventional furnace and the rapid thermal processor. The rapid thermal processor was successfully implemented in a p‐i‐n optical detector process resulting in a reduction in the device series resistance and improved performance.

High Speed 1.31µm InGaAsP Lasers With Semi-Insulating Current-Blocking Layers: Experiment And Modeling

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.

Optimization of grating depth and layer thicknesses for DFB lasers

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.

U-groove distributed-feedback lasers

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.

High-frequency 1.3 um InGaAsP semi-insulating buried crescent lasers for analog applications

The fabrication and performance of high-speed and low relative intensity noise (RIN) 1.3 micrometers InGaAsP semi-insulating buried crescent (SIBC) Fabry-Perot (FP) lasers with Zn- doped active layers are reported. These SIBC lasers have a 3-dB modulation bandwidth of 19 GHz for pulsed operation and 16 GHz for cw operation, and a RIN below -150 dB/Hz for biased current at 120 mA. This is the highest modulation bandwidth yet reported for InGaAsP lasers with semi-insulating current blocking layers.

Effect of active layer doping on static and dynamic performance of 1.3-um InGaAsP lasers with semi-insulating current blocking layers

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.