Tongnian Sun

Characterization of defects and whole wafer uniformity of annealed undoped semi-insulating InP wafers

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

H-vacancy complex VInH4 abundance and its influences in n-type LEC 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.

Native donors and compensation in Fe-doped liquid encapsulated Czochralski InP

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...

Carrier mobility distribution in annealed undoped LEC InP material

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.

Hydrogen neutralization effect in bulk N-type LEC InP materials

Abstract 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.

Synthesis of indium phosphide polycrystalline

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.

The Preparation of Large diameter Twin-free InP Crystals

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

Recent research results on deep level defects in semi-insulating InP-application to improve material quality

An apparent defect suppression effect has been observed in InP through an investigation of deep level defects in different semi-insulating (SI) InP materials. Quality improvement of SI-InP based on the defect suppression mechanism is presented

Character of non-stoichiometric InP bulk crystal

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.

Homogeneity study of wafers of InP single crystal grown from P-rich melt

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.