DE10319972B4 - Process for producing an epitaxial ZnO layer - Google Patents

Abstract

A process for producing a ZnO epitaxial layer by depositing the ZnO layer with dimethylzinc or diethylzinc as a Zn precursor, characterized by the simultaneous use of a gaseous inorganic oxygen precursor selected from the group consisting of N ₂ O, NO or NO ₂ and an organic oxygen precursor in the Form of an aliphatic alcohol having 1 to 14 carbon atoms.

Description

The The invention relates to a method for producing an epitaxial ZnO layer by depositing the ZnO layer with dimethylzinc or diethylzinc as Zn precursor.

in the further text the following abbreviations are used:

Abbreviations

• Zn

  zinc

  mg

  magnesium

  CD

  cadmium

  al

  aluminum

  ga

  gallium

  In

  indium

  Group II

  Elements from the II. Main or subgroup

  O

  oxygen

  C

  carbon

  N

  nitrogen

  H

  hydrogen

  GaN

  Gallium nitride

  R

  an inorganic one or organic rest

  M

  OCVD organometallic Gas phase epitaxy, also called MOVPE

  MBE

  Molecular Beam Epitaxy; All related methods like MO-MBE or GS-MBE are also included here

  VPE

  Vapor Phase Epitaxy, sometimes known as HVPE or CVD

  LED

  Light emitting diode (Light emitting diode)

The epitaxial growth of Group II-O semiconductors such as e.g. ZnO, CdO or MgO on homo or hetero substrates is currently becoming intense researched since it was supposed to achieve p-type doping [e.g., Eagle-Picher press release, EAGLE-PICHER Demonstrated p-type doping in ZnO, http://www.tech.epcorp.com/news/010702.htm, January 7, 2002; or D. C. Look, et. al, Characterization of homoepitaxial p-type ZnO grown by molecular beam epitaxy, Applied Physics Letters 81, 1830 (2002)]. With the successful p-type doping is the production of ZnO-based electronic and optoelectronic Components to many possibilities been extended. It is except the commonly used sputtering in particular the epitaxial deposition of ZnO with MBE, MOCVD or VPE for the industrial mass production of e.g. ZnO-based LEDs very much Interesting. Here, however, often poses the problem that the layer growth either on heterosubstrates or even on homosubstrates badly disturbed begins and no smooth, device-suitable layers can be achieved can. reasons can except the differences in the surface energy for heterosubstrates, e.g. GaN templates on sapphire, also disturbing oxides or ZnO single crystal surface passivation with OH groups, but what is still the subject of research.

For the p-type doping of ZnO, inter alia, the introduction of nitrogen into the crystal is necessary, which is easily possible by means of ammonia or in the MBE with N radicals. In particular, when using ammonia, a high growth temperature is indicated because ammonia decomposes only poorly thermally due to its high binding energy. In gas phase epitaxy, in principle, the layer growth with precursors such as N ₂ O, NO, NO ₂ , CO or CO _{2 is} possible, which decomposes thermally poorly, which is why higher growth temperatures are necessary for crystal growth.

For the production of epitaxial ZnO layers, the use of dimethylzinc or diethylzinc as Zn precursor and various inorganic oxygen precursors and H ₂ O and alcohols as oxygen precursors is also known [Sh. Oda et al., Highly Oriented ZnO films prepared by MOCVD from Diethylzinc and alcohols, Jpn. J. Appl. Phys. Vol. 24, (1985) 1607-1610]. However, this publication does not suggest to simultaneously use a gaseous inorganic oxygen precursor such as N ₂ O, NO or NO ₂ and an organic oxygen precursor in the form of an alcohol at a temperature in the range of about 0 ° C to 40 ° C.

Generally is a high growth temperature for ZnO growth alone because of this preferable because of because of an II-VI Semiconductor high binding energy so easier high Adatommobilität and thus a smooth surface can be achieved.

At the Growth of Group II Oxides at Higher Temperatures Appears even if low-temperature buffer layers are used, only difficult smooth, continuous layers can be achieved.

The The above-mentioned disadvantages are intended to be overcome by the invention become.

According to the invention this is by a method according to claim 1 reached.

Claim 1 describes the possibility at high growth temperatures to obtain a homogeneous and smooth ZnO layer by using as Zn precursor dimethylzinc or diethylzinc and a gaseous an inorganic oxygen precursor selected from the group consisting of N ₂ O, NO or NO ₂ , to which is simultaneously added to an organic oxygen precursor in the form of an aliphatic alcohol having from 1 to 14 carbon atoms. The addition of the organic oxygen precursor significantly improves the morphology of the layer.

The following is a brief description of the possible Schichtwachtsums in the MOCVD as an embodiment: For this example, a hetero substrate such as GaN is loaded on sapphire in the reactor and heated to about 450 ° C under a carrier gas such as H ₂ or N ₂ . To start the layer growth is according to claim 2 and such. B. in the DE 10 238 135 A1 first, a buffer layer grown at a lower temperature than the deposition temperature of the main layer. For this purpose, the Zn source, usually dimethylzinc or diethylzinc and the oxygen source such as tertiary-butanol is opened and deposited for a few minutes at a high VI-II ratio in the gas phase (much greater than 1), an approximately 100 nm thick ZnO layer , Thereafter, the heating takes place at about 900-950 ° C, preferably under nitrogen and the Hochtemperatursohstoffprecursor such as N ₂ O. In this case, the tertiary-butanol source is opened to better during the transition from low to high temperatures, the ZnO surface stabilize. The main layer growth then takes place under N ₂ O and tert-butanol, usually with a lower tert-butanol flow than in the buffer layer, and dimethylzinc or diethylzinc, preferably in an inert gas atmosphere, eg N ₂ . The layer thus obtained is smooth and of high crystalline quality and thus suitable for component structures, for which they may still have to be doped. For p-type doping suitable for this purpose according to claim 3, the use of nitrogen, for example as in claim 4 in the form of ammonia or claim 5 an R-hydrazine with R none, one or more arbitrary organic radicals such. B. Dimethylhydrazine. For n-type doping, the usual doping with Ga, Al or In using z. As trimethylgallium, - aluminum or - indium used.

Claims (5)

A process for producing a ZnO epitaxial layer by depositing the ZnO layer with dimethylzinc or diethylzinc as a Zn precursor, characterized by the simultaneous use of a gaseous inorganic oxygen precursor selected from the group consisting of N ₂ O, NO or NO ₂ and an organic oxygen precursor in the Form of an aliphatic alcohol having 1 to 14 carbon atoms. Method according to claim 1, characterized by Growing a low-temperature buffer layer in front of the main layer. A method according to claim 1 or 2, characterized by doping with nitrogen. A method according to claim 1, 2 or 3, characterized by using ammonia for nitrogen doping. The method of claim 1, 2, 3 or 4, characterized by using hydrazines for nitrogen doping.