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Indium (In) inclusions have been found in 〈100〉 indium phosphide (InP) single crystals grown in In-rich melt by the liquid-encapsulated Czochralski (LEC) method. Two kinds of In inclusions with different morphologies, one is lath-like and the other is polyhedral, have been observed. Most of the In inclusions are lath-like and their long sides are always parallel to the $$[0\overline{1}1]$$ or $$[0{\overline{1}}{\overline{1}}]$$ orientation. In (100) InP wafers, these inclusions mainly distribute in two regions viz., center of the wafer and annular belt at a certain distance from the center. These special distributions of In inclusions in InP crystals were found in our experiments for the first time. In order to clarify the cause of the special distributions of In inclusions, numerical simulations have been carried out on the melt convection in the process of InP crystal growth. The results show that the rotations of crystal and crucible significantly affect the number and direction of convection cells in the melt, which have a great influence on the enrichment and distribution of excess In at the solid–liquid interface. Different melt convections modify the radial distributions of excess In atoms near the solid–liquid interface and result in different radial distributions of In inclusions in the crystals.

In this paper, indium (In)-rich second-phase particles are observed in InP crystals, which is induced by the loss of phosphorus (P) during polycrystalline melting. Their characterizations reveal that the size of these In-rich particles is 200 nm–20 µm. The dislocation structure surrounding the second-phase particle and its formation is explained by the model of prismatic dislocation loop. The indium-rich second-phase particles could be eliminated under P-rich condition by a rapid in situ P injection before crystal growth. Excessive P injection will lead to the formation of P pores with internal P deposits. The optimal injection value is given to eliminate the defects.

The two dimension distributions of dislocation and thermal stress of 3-inch diameter stoichiometric and P-rich InP wafers are investigated, and an analysis of the relation between the two distributions is given. As a result, in stoichiometric and P-rich InP wafers, both the dislocation and thermal stress distributions are found to be circular ring shape, and where the thermal stress is stronger, the etch-pits density (EPD) is higher, too. On the P-rich wafers, there are some pores where EPD is much higher than other areas, around most pores, thermal stress is very strong, but around a small number of pores, the thermal stress is weaker as a contrary, that may be because the residual thermal stress can be released along the pores penetrating through the ingot during ingot annealing. Thermal stress is one of the main reasons which can contribute to dislocation. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We present the investigation of twinning phenomena of LEC InP crystal growth which has been carried out in our laboratory in recent years. It is observed that the yield of twin-free single crystal InP can be grown by control the cone angle and crystal shape of a gradually increased diameter. Twin formation has been correlated to many growth factors. The influence of ingot shape on the formation of twins can be looked as the conical angle dependent twin probability of InP crystals. Twin-free InP crystals can be grown by large cone angle over 75° to 90°. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Positron lifetime measurements have been carried out on liquid-encapsulated Czochralski-grown undoped InP samples sliced from the middle part of ingots over the temperature range 10–300 K. And at 70 K, the spectra have been measured in darkness, under illumination of infrared LED, and with illumination off is one sample. The measurements at low temperature reveal different concentration of hydrogen indium vacancy complex VInH4 in these samples. A relatively higher concentration of VInH4 in samples grown from P-rich undoped InP melts can be shown. The increase of resistivity of these samples can be speculated when temperature is low enough.

Undoped, S-doped and Fe-doped InP crystals with diameter up to 4-inch have been pulled in drop 10 0 drop -direction under P-rich condition by a rapid P-injection in situ synthesis liquid encapsulated Czochralski (LEC) method. High speed photoluminescence mapping, etch-pit density (EPD) mapping and scanning electron microscopy have been used to characterize the samples of the single crystal ingots. Dislocations and electrical homogeneity of these samples are investigated and compared. By controlling the thermal field and the solid-liquid interface shape, 4-inch low-EPD InP single crystals have been successfully grown by the rapid P-injection synthesis LEC method. The EPD across the wafer of the ingots is less than 5 x 10(4) cm(-2). Cluster defects with a pore center are observed in the P-rich LEC grown InP ingots. These defects are distributed irregularly on a wafer and are surrounded by a high concentration of dislocations. The uniformity of the PL intensity across the wafer is influenced by these defects. (C) 2004 Elsevier B.V. All rights reserved.

Semi-insulating (SI) InP wafers of 2 and 3 in. diameters have been prepared by annealing undoped LEC InP at 930 degreesC for 80 h under pure phosphorus ambient (PP) and iron phosphide ambient (IP). The electrical uniformity of annealed undoped SI wafers, along with a Fe-doped as-grown SI LEC InP wafer, has been characterized by whole wafer PL mapping and radial Hall measurements. Defects in these wafers have been detected by photo-induced current transient spectroscopy (PICTS). The results indicated that the uniformity of IP wafer is much better than that of PP wafer and as-grown Fe-doped Si InP wafer. There are fewer traps in undoped SI InP IP wafer than in as grown Fe-doped and undoped SI InP PP wafer, as evidenced by PICTS. The good uniformity of the IP wafer is related to the nonexistence of high concentration of thermally induced defects. The mechanism for this phenomenon is discussed based on the results. (C) 2002 Elsevier Science B.V. All rights reserved.

FTIR spectroscopy measurements indicate a presence of high concentration hydrogen existing in the liquid encapsulated Czochralski grown undoped InP wafers. These undoped InP can be annealed to be semi-insulating (SI) reproducibly. Hydrogen can facilitate the formation of anti-site defects in InP and can also induce electrically-active hydrogen related defects. The annealed behavior of InP is proved possible to be originated from the neutralization effect of hydrogen that is supplied by the dissociation of hydrogen complexes in the process of annealing. The process of hydrogen passivation of donors is discussed. Besides neutralizing impurities and defects in InP, hydrogen induces new hydrogen related defects in the band gap, and can also activate the formation of complexes involving P In , so it plays an important role in the charge compensation process in SI InP obtained by high temperature annealing.

Undoped and Fe-doped liquid encapsulated Czochralski (LEC) InP has been studied by Hall effect, current–voltage (I–V), and infrared absorption (IR) spectroscopy. The results indicate that a native hydrogen vacancy complex donor defect exists in as-grown LEC InP. By studying the IR results, it is found that the concentration of this donor defect in Fe-doped InP is much higher than that in undoped InP. This result is consistent with the observation that a much higher concentration of Fe2+ than the apparent net donor concentration is needed to achieve the semi-insulating (SI) property in InP. By studying the I–V and IR results of Fe-doped InP wafers sliced from different positions on an ingot, the high concentration of Fe2+ is found to correlate with the existence of this hydrogen complex. The concentration of this donor defect is high in wafers from the top of an ingot. Correspondingly, a higher concentration of Fe2+ can be detected in these wafers. These results reveal the influence of the complex defect o...

N-type liquid encapsulated Czochralski (LEC) undoped InP wafers are annealed between 700 and 900 C for different durations. From a large quantity of Hall measurement results, it is found that there is a Hall mobility distribution dependent on the carrier concentration of the annealed material. The lowest mobility is observed in the samples with concentration around ∼ 10 10 cm -3 . In these samples carrier mobility increases with increasing temperature which is caused by nonuniformity. Combined with results of defect investigation in the annealed material, formation of defects and their nonuniform distribution are found to correlate with this mobility distribution. The formation of defect complexes is interpreted as a reason for the high mobility observed in annealed InP.

A hydrogen indium vacancy complex V In H 4 in undoped and Fe-doped liquid encapsulated Czochralski (LEC) InP is measured by infrared absorption spectroscopy in wafers sliced from the seed-end, middle and tail of an ingot. The concentration of V In H 4 is found much lower in wafers sliced from the ingot tail. The concentration of V In H 4 in Fe-doped InP is higher than that of the undoped InP. The concentration change of V In H 4 in an InP ingot is qualitatively in agreement with the mass action law expectation based on defect reactions. The influence of this complex on the electrical properties of n-type LEC undoped and Fe-doped InP is discussed. The high concentration of V In H 4 in the seed-end of an InP ingot correlates with two facts. The first is the high threshold concentrations of Fe and Zn required to get semi-insulating and p-type material, respectively. The second is that there is a large thermally induced reduction of carrier concentration in seed-end InP wafers than that of wafers from the ingot tail. The results reveal the influence of V In H 4 on the thermal stability of InP material due to the fact that the bond of hydrogen complex is weak and dissociates easily upon annealing. This dissociation has a relationship with the defects formed in high-temperature annealed InP, which are involved in the electrical compensation.

We studied the effect of HCl, H3PO4, HBr etchants, temperature, illumination on the display of dislocation pits on InP single crystal wafers, and analyzed the effect of illumination, using the wet chemical etching method. The experimental results show that the etching rate is strongly dependent on the proportion of HBr in the mixed etchant and HBr alone can reveal dislocation pits on InP wafers. Both illumination and higher temperature can increase the etching rate. We also discuss the mechanism of different sizes of dislocation pits.

A large quantity of high purity InP crystal material has been produced by the phosphorus in-situ injection synthesis. In the injection method, phosphorus reacts with indium very quickly so that the rapid polycrystalline synthesis is possible. The injection speed, melt temperature, phosphorus excess, and so on are also important for a successful synthesis process. About 3200-4800 g stoichiometric high purity poly InP is synthesized reproducibly by improved P-injection method in the high-pressure puller. Twin-Free InP single crystals with diameter of 50-110 mm can be pulled after the synthesis. In the present work, the characterization of InP polycrystalline was studied by van der Pauw method, GDMS, and PL.

InP substrates have been indispensable to both optical and electronic devices. The cost reduction in the manufacturing process of these devices and the increase in size of IC chips have strongly required a larger diameter of these substrate wafers. Promoted by this requirement, InP single crystal technology has been rapidly developed. In the present paper, the development and key technology of large diameter twin-free InP crystal growth are discussed

P-rich of InP crystals are rather difficult to achieve, due to the high phosphorus pressure at the melting point. By using the P-injection in-situ synthesis method, there is excessive phosphorus in the melt. In the conditions of M/sub In/ [In]/sub mol/, the melt might be P-rich. Since a high thermal stress exists in the LEC growth process with large temperature gradient, it is difficult to release stress, a large number of dislocations come into being around the pores. The pores are distributed in the ingots irregularly. The diameter of the pores is from

Sn-doped InP is being used as a platform for a wide variety of fiber communications components, including lasers, LEDs, semiconductor optical amplifiers, modulators and photo-detectors. The more the diameter is, the more imperfection of the InP crystal would be. The substrates with large diameter are desired in order to realize low devices cost. In recent years, we have developed a high quality 3-inch and 4-inch Sn-doped InP single crystal growth using the HP-LEC method after P-injection direct synthesis polycrystalline. It is found that by carefully adjusting the thermal symmetry of the heating field and by further improving the quality of the polycrystalline, three inch and four inch twin-free Sn-doped InP crystals can be obtained even with a shoulder angle of up to 35/spl deg/-90/spl deg/, and defects caused by thermal decomposition appear on the surface of the crystals during pulling. For LEC InP crystals, twin formation can be effectively suppressed by optimization of growth conditions, such as thermal field, doping concentration, etc. However, it is difficult to grow twin-free LEC InP in a similar way. It is observed that the yield of single crystal InP can be increased by controlling the ingot shape of a gradually increased diameter.

A 4-inch InP single crystal has been grown from P-rich melt by the P-injection synthesis LEC method. Due to the non-stoichiometric condition, there are many pores in the tail of the ingot. The wafers cut from it are experimented by means of PL mapping and EPD mapping. The PL peak intensity standard deviation of the 4-inch InP wafer is higher. The EPDs around the pores are larger than the other regions. Besides the stress releasing, the pores and the high concentration of dislocations around them presents the leading factors causing the inhomogeneity of the wafer. We have explained the phenomena.

P-rich, In-rich and stoichiometric undoped InP melts have been synthesized by phosphorus in-situ injection method, InP crystal ingots have been grown from these melts by LEC method. The difference in these InP crystal should be attributed to the change of stoichiometry. Some samples from these ingots have been characterized by the Hall effect and Fourier transform infrared (FT-IR) spectroscopy measurements respectively. The Hall effect measurement results indicate that the carrier concentration of P-rich undoped InP is higher than that of In-rich and stoichiometric undoped InP materials. The intensive absorption peaks indicate that our phosphorus in-situ injection synthesis LEC undoped InP materials have relatively high concentration of hydrogen related complexes. The FT-IR results are also in agreement with the carrier concentration of InP grown from different stoichiometric melts.

Semi-Insulating InP is used in microelectronics devices and integrated opto-electronic circuits. The Chinese InP research team used a direct P-injection synthesis and LEC crystal growth method to prepare polycrystalline InP and to grow the undoped InP and Fe-doped SI-InP single crystal in the same puller. We can get very low concentration silicon in the ingots by using this method. And in the InP crystal the main impurity is silicon, which acts as a shallow donor in the crystal. The undoped InP has been found to be annealed into SI material around 900/spl deg/C. The Chinese InP research team present a model to explain the possible mechanisms of the Semi-Insulating behavior of bulk InP material. The physical properties of SI-InP have been studied. We have combined a variety of techniques such as FT-IR, PICTS, Hall, TDH, PL, PAS, and GDMS to investigate SI-InP. Most of the data can be explained by this model. Furthermore we compared the results of the MOCVD material, which grow on the annealed undoped SI-InP and on Fe-doped SI-InP.

High purity InP is necessary for the preparation of high quality InP single crystal especially low Fe content semi-insulating and annealed undoped semi-insulating InP single crystal. In-situ phosphorus injection synthesis of InP has several advantages over the two-step process of compounding and growing in separate furnace. In 1982 it was reported by our group that around 500g InP was synthesized and semi-insulating InP single crystals grown in one step in 30-60 minutes. A large high pressure puller have been set up, which can be used to synthesize and grow large diameter InP single crystal in our laboratory. Now 3400g InP can be synthesized reproducible and single crystals can be grown in the puller. The red phosphorus used for synthesis is contained in two vessels, which can be manipulated separately during the synthesis process. The two phosphorus vessels are heated by the auxiliary heater and the phosphorus vapour is injected into the indium melt in the crucible. We have developed a process for the rapid synthesis of InP. The whole synthesis process only needs 60-70 minutes. The synthesized InP could be indium-rich, stoichiometric or phosphorus-rich which depend on the quantity of excess phosphorus and other conditions such as the temperature of indium melt in the crucible, the thermal field, phosphorus injection speed etc. After the synthesis, InP crystal can be pulled by the conventional LEC method. Twin-free 3-inch and 4-inch InP single crystal can be obtained. The InP single crystal wafer is cut from the ingot for the measurement of electronic parameters. The carrier concentration of P-injection in-situ synthesis InP at T = 300 K is n = 2 /spl times/ 10/sup 15/ - 10/sup 16/ cm/sup -3/, the mobility is 3500 4900 cm/sup 2//Vs. These depend on the raw materials used. At T = 77 K the best result n = 2.36 /spl times/ 10/sup 15/ cm/sup -3/, the mobility is 4.8 /spl times/ 10/sup 4/ cm/sup 2//Vs. This kind of InP can be made semi-insulating with high temperature annealing or low iron doping levels.

A large quantity of high purity InP crystal material has been produced by the phosphorus in-situ injection synthesis and liquid encapsulated Czochralski (LEC) growth process. The in-situ process exhibits several advantages over the two-step process of compounding and growing in separate furnaces. About 2500-5000g stoichiometric poly InP is synthesized reproducibly by P-injection method in the high-pressure puller. Twin-f ree InP single crystals with diameter of 60-100 mm can be pulled after the synthesis.

Undoped liquid encapsulated Czochralski (LEC) InP samples have been studied by Hall effect, glow discharge mass spectroscopy (GDMS) and infrared absorption spectroscopy. A systematic discrepancy has been found between the Hall electron concentration and net donor concentration measured by GDMS. The electron concentration is always higher than the net shallow donor concentration by about (3-6)/spl times/10/sup 15/ cm/sup -3/. A hydrogen indium vacancy complex donor defect V/sub In/H/sub 4/ was detected regularly by infrared absorption spectroscopy in all undoped LEC InP samples. The fact can be explained by taking into account the existence of the donor defect in as-grown undoped LEC-InP.

It has recently been suggested that the thin degenerate layer found at the GaN/sapphire interface results from a high concentration of stacking faults. The studies of this letter, however, show that this is not the most likely explanation for the presence of such a degenerate layer. Using x-ray energy-dispersive spectroscopy and secondary ion-mass spectroscopy, profile distributions of elements Ga, N, O, C, and Al, near the interface, have been obtained. The distributions reveal very high O and Al concentrations in the GaN film within 0.2 μm from the interface, together with a material depletion of Ga and N. Such conditions strongly favor n+ conductivity in this interfacial region because not only are N-vacancy and N-site O donors present, but Al incorporated on the Ga sublattice reduces the concentration of compensating Ga-vacancy acceptors. The two-layer (film plus interface) conduction has been modeled, and the effect of conduction in the GaN film thus isolated.