Elsevier

Journal of Crystal Growth

Volume 233, Issue 4, December 2001, Pages 631-638
Journal of Crystal Growth

Growth of bulk Ga1−xMnxN single crystals

https://doi.org/10.1016/S0022-0248(01)01593-7Get rights and content

Abstract

Mixtures of powders of gallium nitride and manganese were annealed in a stream of ammonia at temperatures from the range of 1200–1250°C. The procedure resulted in preparation of bulk single crystals of gallium nitride of dimensions up to 2.7×1.5×0.5 mm and containing up to 2% of Mn by weight. The influence of temperature, ammonia flow rate and manganese concentration in the substrate material on the doping level of the obtained bulk crystals was studied. The concentration of manganese was determined by means of an electron microprobe method. Raman investigations supported the conclusion on the well ordered structure of the prepared crystals. The measurements done by a superconducting quantum interferometer showed that the crystals doped with manganese ions manifested paramagnetic properties.

Introduction

A rapid and extensive development of gallium nitride technology is observed in recent years. This material is applied in blue light emitting diodes and lasers [1], [2], [3]. It can be also used for integrated circuits operating at elevated temperatures of about 300°C [4]. Our previous investigations showed that manganese doped GaN gained paramagnetic properties resulting in additional applications. The high concentration of magnetic ions possibly allows for exploitation of the material in magneto-optic devices.

Until now bulk GaN single crystals were intentionally doped with magnesium, only that significantly improved their properties [5].

Section snippets

Experimental procedure

The reagents applied were as follows. Gallium of 99.9999% purity manufactured by SNP Ziar Czech Republic, ammonia of 99.99% purity in a steel cylinder manufactured by Zakłady Azotowe Puławy, Poland, manganese of 99.995% purity manufactured by Koch—Light Laboratories Ltd., England and nitrogen of 99.9995% purity in a steel cylinder manufactured by Multax, Poland.

The synthesis reactions were carried out in a quartz or mullite tube reactor of 59 mm diameter at a temperature range of 1200–1270°C.

The

Preparation of GaN powder

It has been found that good quality GaN crystals heavily doped with manganese can be obtained in a two-stage process. The first step relies on transformation of metallic gallium into polycrystalline gallium nitride powder [6].

About 10 g of gallium was heated at 1200°C for 4 h in a mullite or quartz tube reactor in an atmosphere of a nitriding reagent—ammonia flowing at a rate of 100 l/h [6]. Gallium nitride powder of steel grey colour was obtained in this process. Since this product contained some

Determination of manganese concentration in gallium nitride crystals

The introduction of the dopant in the form of powdered manganese caused differences in shape of the growing crystals. It was observed that platelets comprising about 2% of manganese by weight were growing instead of needles characteristic of the undoped system in comparable conditions.

The Ga1−xMnxN single crystals were prepared in a series of technological processes at different:

  • temperatures,

  • ammonia flow rates,

  • amounts of manganese dopant initially introduced into the system.

Fig. 2 presents the

Conclusions

The conditions of synthesis of good quality gallium nitride single crystals doped with manganese were elaborated. The influence of temperature, ammonia flow rate and initial amount of manganese in the reaction mixture on the dopant concentration in the product were determined.

The performed investigations proved that the studied material—Ga1−xMnxN exhibits typical paramagnetic properties. Despite the intensive investigations carried recently on doped single crystals of gallium nitride there is

Acknowledgements

The work was partially sponsored by KBN (Poland) Grants: 7T08A03514 and 7T08A00719.

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