Deliverable D.6.11 – Version 1

Contract number 027455

HYPHEN

Hybrid Substrates for Competitive High Frequency Electronics

STREP, Specific Targeted Research Project IST-FET Open, Information Society Technology – Future Emerging Technology

Deliverable D 6.11– Deliverable/Report

Public report on the layers grown on SiC/pSiC composite substrates by MOCVD

and by MBE

Workpackage WP 6 – Dissemination and Use

Task 6.1 - Dissemination

Month of delivery: M22

Deliverable leader: MFA

Decisional Workflow Author(s) B. Pecz

Reviewer (s) P. Bove

Scientific Director

Approved by:

WP leader Task leader Scientific Director Project Technical Assessor (European

Commission) Project Officer (European Commission)

Deliverable D.6.11 – Version 1

Description of work (contract)

Objective of the WP: WP6 of the project aims at investigating the economic aspects of the solutions developed and demonstrated in WP 1 to 4. Indeed, if a global agreement exists today on the technical interest of GaN based devices for high power RF applications, the ability of these devices to meet the price objectives for various market segments or applications as tentatively described in the figures below, is still questionable. This task aims at ensuring the largest dissemination of the project scientific and

technological results through participations at Congress, Workshop (organisation),

When appropriate the academic participants shall promote the HYPHEN project results by incorporate these results in high level courses at Universities

In a broader approach the consortium will participate to broader scientific communication and events in their respective regions and countries.

Keep the scientific community, public and the policy bodies informed about HYPHEN achievements

Deliverable D.6.11 – Version 1

Document identifier: Status: v. Creation : / / Contractual deadline: 31/07/2007 (M22) Dependency Delay

Contractual deliverable: Y N Content protection: Y N Access rights: Y N Archive Dissemination level:

PU Public PP Restricted to other programme participants (including the Commission Services) RE Restricted to a group specified by the consortium (including the Commission

Services)

CO Confidential, only for members of the consortium (including the Commission Services)

When Who Registration To do

/ / Y N / / Y N / / Y N / / Y N

Quality Assessment WP Leader Scientific Director PTA (European Commission) Project Officer (European Commission)

Deliverable D.6.11 – Version 1

Contingency Plan

Identified Risks Responsible Consequences Solutions and

Quality control

Resources in person-months

Partner Estimated Resources

Allocated Resources

Picogiga MM MM DEI MM MM III-V Lab MM MM MFA 0,1MM MM Norstel MM MM IET MM MM IEMN- MM MM

Resources shown in person-months

Partner X 0.5 Peer reviews Contributions

UMS MM MM If any difference between estimated resources and allocated resources, please justify:

Results achieved Explain here the results that have been achieved so far and differences between the plan work and final results.

Deliverable D.6.11 – Version 1

Deliverable Technical Description

MOCVD grown HEMT structures AEC1308 on bulk SiC (reference sample)

Overview of the MOCVD grown layers on bulk 4H-SiC. This is an essential reference sample. Defect density measured on this kind of samples is also expected to be achieved when layers are grown onto SiCopSiC substrates.

BF and DF micrographs of SiC/GaAlxN/GaN interfaces

Deliverable D.6.11 – Version 1

Near-substrate region seen from 1120 direction: Most of the dislocations are restricted to the buffer layer, only a few threading dislocations emerge to the film surface.

BF and DF image of GaAlxN/GaN interface in the top region of AEC 1308

The main defects are threading dislocations. The interfaces are sharp and the mirror-like surface is flat. AEC1314 on SiCopSiC

Overview of the sample. Homogeneously thick hexagonal SiC stripe is transferred onto the polycrystalline SiC base material. Most of the defects are concentrated to the buffer layer region and only few threading dislocations emerge to the top surface. The measured thickness of the top GaAlN layer (24 nm) is in agreement (within 1 nm) with the nominal thickness.

Deliverable D.6.11 – Version 1

Cross sectional electron diffraction pattern of sample AEC1314 showing the epitaxial orientation relationship of GaN layer to 6H-SiC. (Miller indices on the right correspond to SiC, while those on the left belong to GaN.) The same epitaxial relationships can be read, as for the former layer grown on bulk SiC. Very good matching of the lattices can be observed.

HRTEM micrograph of the GaAlN/SiC-6H interface. Relatively defect-free, but not very smooth interface can be seen. Measurements of the surface roughness on SiCopSiC substrates resulted in typical rms values of 3 nm.

Deliverable D.6.11 – Version 1

AEC1314; TEM image and EFTEM (elemental maps) of the sample, showing a wavy GaAlN/SiC-6H interface. Looking at these images we should point out, the completely flat top surface of the layered structure, which was shown above. Also the AFM measurements carried out by III-V Lab. on the grown epitaxial layers gave an excellent flatness with rms values of 0.34 nm. Summary of TEM characterization of MOCVD grown GaN/SiCopSiC

• The MOCVD Ga(Al)N layers are single crystalline, the samples were found very similar in microstructure.

• All layers are epitaxially oriented to the substrate (and to each other). • Their observed interfaces are sharp. In spite of the slightly wavy surface of

the composite substrate the top surface is quite planar. • The main crystallographic defects in the GaN films (and also in the HEMT

structure) are threading dislocations starting at the buffer layer. Their density measured at the top surface is 1.0 – 1.6*10-9 cm-2 , much lower than in the nucleation layer.

Deliverable D.6.11 – Version 1

MBE grown layers on SiCopSiC L898

Overview of the structure. The composite substrate is defect-free. However, the threading dislocation density is definitely higher, than in the former (MOCVD grown) layers. This fact does not hinder the growth of superlattice structure in the, as it will be shown later.

BF and DF images

Deliverable D.6.11 – Version 1

High magnification TEM image of the top region of the cross sectional specimen shows the fine structure of the active layers Dislocation density measured on plan view specimens resulted in a value of 10.9 ± 0.8 x 109cm-2 for the HEMT structure MBE grown onto 2” SiCopSiC substrate. MBE was used to grow GaN layers onto various substrates including high purity Si (HPSI), SICOI, etc. Makyoh topography was also measured and bow was determined on several samples from which MFA was supported by whole wafers. An HEMT structure grown on HPSI is shown here, only

Electron diffraction pattern of the interface region shows perfect epitaxy. The orientation relationship was found the same as before: (0001)GaN||(111)Si [1120]GaN||[011]Si

GaN layer grown on a 3” wafer of HPSI.

Deliverable D.6.11 – Version 1

Conclusions:

• Both MBE and MOCVD layers are grown successfully onto SiCopSiC composite substrates.

• Although in some cases the SiC/nitride interface is not completely even the top surfaces are always mirror-like and flat.

• MOCVD is very reproducible and gives lower defect density than MBE. Defect density values down to 1x109 cm-2 are achieved in MOCVD grown samples while about 10x109 cm-2 is determined in the MBE grown epitaxial layers.

• Laterally homogeneous superlattices were grown by MBE showing that the growth can be regulated very precisely.