Zn-doped InP Research Articles

Increase in photoluminescence of Zn-doped p-type InP after hydrogenation

We report on the effect of hydrogenation on the lowtempeTature (5.5 K) photoluminescence properties of Zndoped p-type (p ∼ 3 × 1018cm-3) InP substrates. The photoluminescence spectrum of the as-grown sample shows a ZnIn acceptor-related transition near the band-edge at l.386eV, a Zn-related PL band at l.214eV and a phosphorus vacancy Vp-related PL band at 1.01 eV. After hydrogenation of the samples by exposure to hydrogen plasma, which completely passivates the ZnIn acceptors over a depth of more than 1μ, the deep luminescence bands (1.214 and 1.01eV) disappeared, with a concomitant ∼ 2000-fold increase in the intensity of the near-band-edge emission. Such a large increase in radiative efficiency together with the elimination of the deep luminescence bands indicates hydrogen passivation of deep nonradiative centers in addition to passivation of shallow acceptors.

Deep-level transient spectroscopy studies of near-surface hole and electron traps in Zn-doped InP using high barrier Yb/p-InP Schottky diodes

High barrier Yb/p-InP Schottky diodes were used to study hole and electron traps in Zn-doped p-InP single crystals by deep-level transient spectroscopy (DLTS). DLTS spectra were recorded at different quiescent bias voltages in the temperature range between 80 and 450 K. From the DLTS measurements at reverse bias of 3 V, three hole traps, H1 (EV +0.56 eV), H2 (EV +0.22 eV), H3 (EV +0.12 eV), and one electron trap, E1 (EC −0.40 eV) were observed. The concentration of the traps ranged between 1012 and 1015 cm−3 with a capture cross section between 10−19 and 10−17 cm2. The DLTS spectra, at a quiescent forward bias of 0.2 V, revealed only one interfacial hole trap (EV +0.25 eV) which was different from the hole trap H2 . The measurements at different reverse bias values on the most prominent hole trap indicated an anomalous field dependence of the DLTS signal which suggested that the concentration of the trap level decreased and its activation energy as well as capture cross section increased with depth from the metal–semiconductor junction.

Electrothermomigration and filament growth in p-InP with Au contacts

Metal migration induced by electric field and temperature gradients has been studied in Zn-doped InP with Au contacts. A new failure mode has been observed which involves a temperature-induced decomposition of InP, followed by the formation of a liquid filament nucleating at the negative Au contact. The filament subsequently grows to short out the two contacts. Two forms of filaments are observed; type I is straight and narrow and contains no Au, whereas type II is broader, propagates more slowly, and contains Au. An explanation is presented to rationalize the results.

Characterization of the grown-in defects in Zn-doped InP

Studies of the effect of low temperature thermal annealing (170 °C) and laser annealing on grown-in defects in LEC grown Zn-doped InP have been made using the DLTS technique. One hole trap with energy of E v+∅.52 eV and density of 1.8×10∅ 15 cm −3 was observed in these InP samples. The potential well for this hole trap was determined by comparing the calculated field dependent emission rates with the field enhanced emission rate data obtained from the DLTS measurements. The results show that the potential well for this hole trap may be due to either a Dirac well or a square well, and hence the physical origin for this hole trap is attributed to either a phosphorus vacancy or a phosphorus interstitial related defect.

Electrical and optical properties of Mg-, Ca-, and Zn-doped InP crystals grown by the synthesis, solute diffusion technique

p-type InP crystals doped with Mg, Ca, and Zn have been grown by the synthesis, solute diffusion (SSD) technique. Distribution coefficients for the Mg and Ca in the SSD-grown InP were determined to be 0.20 and 0.025, respectively. 4.2 K photoluminescence emission peaks have also been investigated for Mg-, Ca-, and Zn-doped samples. The binding energy is determined to be EA (Mg)=40 meV, EA (Ca)=43 meV, and EA (Zn)=47 meV. Comparison of the emission peak energies between impurity-doped and nominally-undoped InP shows that Mg and Ca as well as Zn are incorporated as residual shallow acceptors in the high-purity SSD-grown InP (ND−NA ≤1015 cm−3 at 300 K).

A study of zinc doping in metallo-organic chemical vapor deposition of InP

Zn-doped InP epitaxial layers, grown by atmospheric pressure metallo-organic chemical vapor deposition using the adduct process, have been characterized by Hall effect, secondary ion mass spectroscopy, and electrochemical profilling techniques. From the results of these measurements the dopant vapor concentration dependence of the room temperature carrier density, net acceptor density, and total Zn atomic density in the layers has been ascertained and the activation energy of the main acceptor level has been measured as 30 meV. A novel technique for measuring the extent of dopant diffusion is described and this has been used to determine diffusion coefficients of Zn of 1–6×10−13 cm2 s−1, values which are much lower than those previously reported. p-n homojunction devices have also been fabricated and these were evaluated by I-V and C-V measurements. The classical diode equation was obeyed over large ranges of current, and ideality factors for the diodes were found to be 1.2–1.5. These results, together with the C-V measurements, show that high quality InP homojunctions can be produced by the adduct technique and the successful use of the material in advanced devices indicates that this is a valuable process for the future.

Electrical properties of epitaxial indium phosphide films grown by metalorganic chemical vapor deposition

Charge transport properties of epitaxial indium phosphide films deposited on semi-insulating single-crystal InP:Fe substrates by metal-organic chemical vapor deposition were investigated by means of Hall effect and resistivity measurements made over a range of temperature from ∼420 °K down to liquid-nitrogen temperature. The activation energies characteristic of both undoped and acceptor-doped films were found from the variation of carrier concentration in the films with sample temperature. For undoped n-type InP films grown on InP:Fe substrates of the three orientations (100), (111A), and (111B) very small activation energies, ranging from 0.006 to 0.009 eV, were found, although some evidence of deeper levels was also obtained. Zn-doped and Cd-doped InP films were also characterized. The activation energy of Zn in p-type InP was 0.023 eV for (100)- and (111B)-oriented films, and Cd energies were 0.049 eV for (100)-oriented films and 0.067 eV for (111A)-oriented films.

Liquid-phase epitaxial growth of InP and InGaAsP alloys

Liquid-phase epitaxy (LPE) has been used to grow high-quality layers of InP and InGaAsP alloys on InP substrates for a wide variety of device-development and physical-measurement applications. An apparatus featuring a transparent furnace and an atmosphere with controlled amounts of H 2, PH 3 and H 2O has proved to be flexible enough for diverse crystal growth requirements. Carrier concentration vs temperature measurements on LPE-grown InP and InGaAsP samples with N D - N A in the low 10 15 cm -3 range show that they contain a moderate concentration of deep donors. There is evidence that these deep donor states also account for a strong peak in the photoluminescence seen in LPE-grown samples. Substrate-orientation studies have shown that critically oriented substrates improve the morphology for growth of heavily Zn-doped InP.

Heat Treatment of Zn-Doped p-Type InP

Heat Treatment of Zn-Doped p-Type InP

Zn-doped vapor-grown InP

Zinc-doped p-type InP layers has been grown by the In/PCl3/H2 technique. It has been shown that the zinc atoms, incorporated during the growth, become electrically active after annealing. By photoluminescence study at 4.2 °K, it has been found that the main transition on the Zn level, in low-doped material, was situated at 1.377 eV; this transition shifts to 1.382 eV in higher-doped material.