Joseph A. Adamski

MLEK crystal growth of large diameter (100) indium phosphide

Abstract Twin-free single crystals of indium phosphide have been grown using the magnetic liquid encapsulated Kyropoulos (MLEK) method. The characteristic features of this growth method which distinguish it from standard LEC growth of InP, are the impurity distribution coefficient, the solid-liquid interface shape, and the dislocation density. InP crystals grown by both LEC and MLEK methods are compared to show the differences in growth characteristics on the microscale as well as on the macroscale.

MLEK crystal growth of (100) indium phosphide

We have used a combined magnetic liquid encapsulated Kyropoulos/Czochralski (MLEK/ MLEC) technique to produce twin-free indium phosphide (InP) crystals. This technique has advantages over the standard LEC method used for commercial production of InP. By stabilizing convective flows with a magnetic field and controlling the angle between solid and liquid, one can grow large diameter twin-free (100) InP crystals; they are shaped with a flat top as is typical for Kyropoulos growth, and then pulled from the magnetically stabilized melt as in Czochralski growth. This shaping method has the benefit of maximizing the number of single crystal wafers which can be sliced from the boule. MLEK InP growth is distinguished from other methods such as LEC and MLEC with respect to solid-liquid interface shape, dislocation density, and impurity distribution. This process has demonstrated that twin-free InP (100) crystals can be consistently grown.

Thermal characterization of the high pressure crystal growth system for in-situ synthesis and growth of InP crystals

Abstract Indium phosphide (InP) is an important substrate material for light-wave communications, opto-electronics and radiation-resistant solar cells. However, the high cost and low productivity of the current two-step InP crystal growth process remains a severe drawback to its commercial applications. This has motivated many researchers to propose and investigate an innovative scheme of one-step synthesis (by injecting phosphorus vapor into the indium melt) and growth of InP crystals by the liquid-encapsulated Czochralski or Kyropoulos technique. For this one-step process to succeed and produce single crystals of uniform quality, it is important to develop a basic understanding of the mechanisms of energy transport and gas flow in a high-pressure crystal growth (HPCG) system. A series of experiments is conducted to characterize the thermal coupling between the melt and the phosphorus injector and to develop an understanding of the buoyancy-induced flow in a HPCG furnace. The gas flow in a high pressure furnace is turbulent and oscillatory, but radiation dominates the heat transfer. Thermal response of the system is therefore quite stable and predictable. The correlation between temperatures at various locations of the phosphorus injector and the melt is very interesting. The heat of reaction also affects the melt temperature. The phase change phenomenon at the bottom of the phosphorus injector seems to be oscillatory in nature. Theoretical estimates of the strength of gas convection and radiation loss by the melt surface are also presented.

Synthesis and growth processes for zinc germanium diphosphide

Abstract Zinc germanium diphosphide (ZnGeP 2 ) has useful properties for wavelength conversion devices in the mid-in-frared (IR) spectral range. It has a high figure of merit as an optical parametric oscillator (OPO) and it also performs efficiently as a frequency doubler. Present crystal growth technology has been restricted to small volume charges because of the pressure limits of quartz containment vessels. The authors discuss a new approach to synthesis based on direct injection of phosphorus through a B 2 O 3 encapsulant and reaction with the zinc germanium melt, resulting in synthesis of a large melt (350 g) of ZnGeP 2 . When crystallization is followed by cooling the congruent melt down through the α-β transition temperature (952°C) as is typical for bulk growth processes, the result is the growth of partially disordered material. An alternative approach for the growth of ZnGeP 2 below the phase transition temperature by chemical vapor transport (CVT) is discussed. The results of crystal growth below the α-β phase transition temperature are reported.

Rapid synthesis of indium phosphide

A process for the high pressure synthesis of InP using an independent temperature control of a three zone furnace incorporating a heat pipe provides a stable temperature profile throughout the synthesis cycle. Internal/external pressure control of the quartz ampoule is maintained by use of a water cooled baffle and a temperature/pressure balancing program. Complete synthesis is achieved in less than five hours.

Magnetically stabilized kyropoulos growth of undoped InP

Abstract The Kyropoulos growth technique has been applied to 700 g charges of InP. Etched wafers show a uniform dislocation density across 70 mm diameter in contrast with the “W” pattern obtained by LEC. Use of an axial magnetic field in Kyropoulos growth reduces the dislocation density by an order of magnitude, to 1×10 4 cm −2 .