Judith Ann Long

Growth of Fe-doped semi-insulating InP by MOCVD

The semi-insulating InP has been grown using ferrocene as a dopant source by low pressure MOCVD. Fe doped semiinsulating InP material whose resistivity is equal to 2.0x10(8)Omega*cm and the breakdown field is Beater than 4.0x10(4)Vcm(-1) has been achieved. It is found that the magnitude of resistivity increases with growing pressure enhancement under keeping TMIn, PH3, ferrocene (Fe(C5H5)(2)) flow constant at 620 degrees C growth temperature. Moreover, the experimental results which resistivity varies with ferrocene mole fraction are given. It is estimated that active Fe doping efficiency; eta, is equal to 8.7x10(-4) at 20mbar growth pressure and 620 degrees C growth temperature by the comparison of calculated and experimental results.

Electrical characterization of Fe‐doped semi‐insulating InP grown by metalorganic chemical vapor deposition

The bulk resistivity of Fe‐doped metalorganic chemical vapor deposited grown epitaxial InP was determined from current‐voltage and capacitance measurements made on Schottky‐diode‐like devices. The current‐voltage data exhibit both an ohmic and a space‐charge‐limited regime, and the capacitance was found to be independent of applied bias. The electrical thickness was obtained from the capacitance using a relationship appropriate for current injection. Data for two samples representing both thin (∼1 μm) and thick (∼9 μm) epitaxial layers are presented. The resistivities were 6.5×107 Ω cm and 2.2×108 Ω cm.

Thermal decomposition of metalorganic compounds used in the MOCVD of InP

Ultraviolet (UV) absorption spectroscopy has been used to monitor the thermal decomposition of Me3In, Me3In · PMe3, and Me3In · PEt3 employed in the metalorganic chemical vapor deposition (MOCVD) of InP. Both PMe3 and PEt3 were stable to 400°C, the high temperature limit of the optical cell. The onset of Me3In pyrolysis was observed at ∼ 270°C, and the activation energy was found to be ∼ 50 kcal/mol. The reversible dissociation of Me3In · PMe3 into its component alkyls occurred below 100°C. Though a similar behavior is presumed for Me3In ·sPEt3, its low vapor pressure precluded a determination of the temperature at which dissociation was complete. For both adducts, spectral changes at ∼ 300°C consistent with pyrolysis of free Me3In were observed. Based on these observations, it is suggested that these adducts prevent the reaction of free Me3In with PH3 only near room temperature, and that the nonvolatile polymer formed by reaction of Me3In with PH3 might be avoided by gas mixing at slightly elevated temperatures. Based on the relative thermal stabilities measured, a reaction sequence occurring for the deposition of InP is presented.

A transmission electron microscope study of iron phosphide precipitates in InP crystals

Abstract A transmission electron microscope was used to study the nature of small (100–250 A) precipitates observed in semi-insulating Fe-doped InP layers grown by metalorganic chemical vapor deposition technique on (001) InP substrates. Since these precipitate particles did not dissolve in a Br-methanol etching solution, it was possible to isolate the particles on a carbon-coated electron microscope grid. Both electron diffraction and X-ray energy dispersive techniques have shown unambiguously that these particles are stoichiometric FeP crystals.

A photoluminescence study of Cd‐related centers in InP

We report detailed studies of the low‐temperature photoluminescence of Cd‐related centers in InP. The samples consisted of Cd‐diffused InP substrates as well as Cd‐doped InP epitaxial layers grown by metalorganic chemical vapor deposition. Besides the previously identified 1.365‐eV band, a new Cd‐related band at a lower photon energy is reported. At 5.5 K, depending upon the excitation intensity, the peak position of this new band lies in the energy range 1.20–1.33 and 1.33–1.34 eV, respectively, in the substrates and in the epitaxial layers and it is broader compared to the 1.365‐eV band. The peak position of the bands shifts to higher energy with increasing excitation intensity but the change in the peak energy per decade change in excitation intensity is much larger (50 meV) for the lower‐energy band compared to the 1–2 meV shift for the 1.365‐eV band. While the excitation dependence of the bands suggests a donor‐to‐acceptor pair recombination for their origin, we present arguments to show that the lar...

A study of Fe-dopants for growth of semi-insulating InP by MOCVD

Abstract SIMS depth profiling has been used to measure the Fe concentrations in Fe-doped InP epitaxial layers, grown by MOCVD, using a variety of dopant sources. Iron-olefin carbonyl sources were found to give smoother and more uniform doping profiles than Fe(C5H5)2, although similar electrical properties were obtainedproviding the Fe concentration was below ∼8×1018 cm−3. For the majority of samples analyzed, resistivities ⩾ 4×107 Ω cm were measured. From the temperature dependence of the resistance of the material, an activation energy of 0.68 eV was calculated, in excellent agreement with the values previously obtained for bulk Fe-doped InP.

Effect of mesa shape on the planarity of InP regrowths performed by atmospheric pressure and low pressure selective metalorganic vapor phase epitaxy

Abstract The effect of mesa shape on the planarity of InP regrowths produced by atmospheric pressure and low pressure (0.1 atm) selective (SiO 2 masked) metalorganic vapor phase epitaxy (MOVPE) is investigated. We find that for two separate atmospheric pressure reactor configurations (vertical and horizontal with a factor of 4 difference in growth rate), relatively planar regrowths are reproducibly obtained only when the mesa is non-reentrant, that is, with the narrowest portion of the mesa at the top in contact with the mask. For reentrant mesas grown at atmospheric pressure, the non-planarity is characterized by a large lateral growth rate at the top of the mesa just underneath the mask and by a very small growth rate underneath the volume of large lateral growth, the combination of which results in deep trenches on the side of the mesa and mask overgrowth from the edges. On the other hand, selective MOVPE at low pressure results in planar regrowths on the same reentrant mesas that had produced extremely non-planar regrowths during atmospheric pressure growth.

Diffusion in InP using evaporated Zn3P2 film with transient annealing

A new diffusion technique in InP using a Zn3P2 layer as the diffusion source with rapid thermal annealing is evaluated, and a number of interesting features are discussed. A p+ layer can only be achieved at temperatures ranging between 500 and 550 °C with a 15‐s minimum diffusion time. Diffusivity is calculated and it is comparable with that of furnace diffusion. However, in order to form a shallow layer, there should not be any high temperature treatment or any other cause for the redistribution of Fe or dopant. Annealing at 850 °C for 15 s prior to diffusion moves the carrier profile from 3000 to 6000 A deep, and the second diffusion front extends to 2.4 μm for the semi‐insulating InP substrate. Similar results are obtained on MOCVD grown semi‐insulating Fe:InP epiwafer. Diffusion performed on samples without preannealing resulted in two diffusion fronts and a 2.8‐μm deep second diffusion front is observed for a diffusion performed on a preannealed epiwafer.

Shallow p+ layer in In0.53Ga0.47As using P/Be and As/Be co-implant

Be is implanted into an n‐InGaAs epitaxial layer. Both electrical and atomic profiles indicate that Be in‐diffusion occurs during annealing, resulting in a p layer thicker than that desired. A co‐implant of P or As with Be significantly reduces this Be in‐diffusion resulting in shallow (2000 A) p+‐n junctions with 4×1018 cm−3 surface hole concentration and 70% electrical efficiency.

A Photoluminescence Study of Cd Related Centers in InP

We report the results of a low temperature photoluminescence study of Cd related centers in InP. Besides the previously identified 1.365 eV band a new Cd related band is reported. The peak position of this band lies in the energy ranqe 1.2-1.3 eV at 5.5K dependinq upon the excitation intensity. The peak position of the bands shifts to higher energy with increasing excitation intensity but the change in the peak energy per decade chanqe in excitation intensity is much larger (50 meV) for the lower energy band compared to the 1-2 meV shift for the 1.365 eV band. Both bands exhibit thermal quenching of luminescence above lOOK with an activation energy of 54±4 meV which is comparable to the ionization energy for the substitutional Cd acceptor, Cd In . From this we infer that both bands involve the Cd In acceptor in the recombination process. While the excitation dependence of the bands suggests a donor-to-acceptor pair recombinaton for their origin, we present arguments to show that the larger shift of the peak energy of the 1.2-1.3 eV band with excitation intensity is perhaps a consequence of the involvement of a deep donor in its origin as opposed to a shallow donor in the 1.365 eV band. It is suggested that the deep donor is related to Cd and possible centers are discussed.