D. Renner

Selective growth of InP on patterned, nonplanar InP substrates by low-pressure organometallic vapor phase epitaxy

The effects of indium sources, mask materials and etched mesa profiles on growth mor-phology of Fe-doped semi-insulating InP on patterned, nonplanar InP substrates were studied for low-pressure organometallic vapor phase epitaxy (OMVPE). The presence or absence of polycrystalline InP layers deposited on the mask was found to depend on the indium source but not on the mask material. Trimethylindium was found to be the preferable indium source for prevention of polycrystalline InP deposits on the mask. The etched mesa shape was found to dominate the final geometry of the OMVPE re-grown InP layer. Inclusion of an interfacial layer of 1.16 µm bandgap wavelength InGaAsP between the dielectric mask and InP substrate produces a favorable mesa shape by con-trolling the level of undercut during mesa etching, so as to form a smooth mesa profile. After selective regrowth of InP over the resulting mesa, a planar surface is typically achieved for mesa stripes with a mask overhang length as long as 2.6 µm and a mesa height as high as 4 µm.

High‐speed and high‐power 1.3‐μm InGaAsP buried crescent injection lasers with semi‐insulating current blocking layers

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.

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...

Low threshold 1.51 μm InGaAsP buried crescent injection lasers with semi‐insulating current confinement layer

A hybrid growth technique has been used to fabricate low threshold 1.51 μm InGaAsP buried crescent injection lasers with a semi‐insulating current confinement layer. The technique involves a first stage of low pressure metalorganic chemical vapor deposition followed by a liquid phase epitaxy stage. The 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 has been obtained. The 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.

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 active layer thickness on differential quantum efficiency of 1.3 and 1.55 μm InGaAsP injection lasers

The dependence of differential quantum efficiency (ηd) on active layer thickness (d) for 1.3 and 1.55 μm InGaAsP buried crescent (BC) injection lasers has been measured. A comparison of the results shows that ηd for 1.55 μm lasers increases more rapidly with decreasing d than ηd for 1.3 μm lasers. The significantly different dependence of ηd on d in BC lasers suggests that the optical absorption in the active region of InGaAsP lasers is strongly wavelength dependent. This gives the important practical conclusion that the ηd for 1.55 μm lasers can be significantly improved by reducing d, whereas the ηd for 1.3 μm lasers can only be slightly improved by reducing d. As a result of ηd vs d investigation, we have obtained high performance 1.3 and 1.55 μm BC lasers which exhibit threshold currents as low as 9 mA at 25 °C, high‐temperature operation (up to 100 °C), and ηd over 65% (1.3 μm) and 45% (1.55 μm).

Low‐threshold and wide‐bandwidth 1.3 μm InGaAsP buried crescent injection lasers with semi‐insulating current confinement layers

A hybrid growth technique has been used to fabricate low‐threshold, high‐modulation bandwidth, and high‐power 1.3 μm InGaAsP buried crescent injection lasers. The technique involves a first growth of an Fe‐doped semi‐insulating current confinement layer by low‐pressure metalorganic chemical vapor deposition followed by a liquid phase epitaxy regrowth. The lasers have cw threshold currents as low as 10 mA at 25 °C, total differential quantum efficiency over 50%, high‐temperature operation up to 100 °C, and output power more than 33 mW/facet. A 3‐dB modulation bandwidth of 8.4 GHz has been achieved at 5 mW/facet.

Dynamic characteristics of semi‐insulating current blocking layers: Application to modulation performance of 1.3‐μm InGaAsP 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.

Effect of active layer thickness on differential quantum efficiency of 1.55 μm InGaAsP buried crescent injection lasers

Comprehensive measurements of the differential quantum efficiency (ηd ) dependence on the active layer thickness (d) for 1.55 μm InGaAsP buried crescent (BC) injection lasers are presented. The results show that ηd increases rapidly as d decreases. The strong d dependence of ηd in 1.55 μm BC lasers suggests that a large value of optical absorption in the active region is one of the dominant mechanisms which determines the ηd of these InGaAsP lasers. The likely cause for large absorption in the active region is intervalence band absorption (IBA). Thus, by reducing the active layer thickness and hence, the effect of IBA, we have obtained 1.55 μm BC lasers which exhibit threshold currents as low as 9 mA at 25 °C, ηd over 45%, and high‐temperature operation up to 100 °C.

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.