Determination of stress in GaAs/Si materialChaorong Li, Zhenhong Mai, Shufan Cui, Junmin Zhou, and Aiju Ding Citation: Journal of Applied Physics 66, 4767 (1989); doi: 10.1063/1.343787 View online: http://dx.doi.org/10.1063/1.343787 View Table of Contents: http://scitation.aip.org/content/aip/journal/jap/66/10?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Growth of stress-released GaAs on GaAs/Si structure by metalorganic chemical vapor deposition Appl. Phys. Lett. 77, 3947 (2000); 10.1063/1.1333691 Cathodoluminescence studies and finite element analysis of thermal stresses in GaAs/Si stripes J. Appl. Phys. 74, 2779 (1993); 10.1063/1.354626 Thermal stresses in squarepatterned GaAs/Si: A finiteelement study Appl. Phys. Lett. 59, 3428 (1991); 10.1063/1.105697 Influence of nucleation procedures on stress relaxation in heterostructures: GaAs/Si(100) Appl. Phys. Lett. 59, 1764 (1991); 10.1063/1.106217 Optical determination of strains in heterostructures: GaAs/Si as an example J. Appl. Phys. 66, 196 (1989); 10.1063/1.343904

[This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

129.24.51.181 On: Fri, 28 Nov 2014 08:36:22

Determination of stress in GaAs/Si material Chaorong Li, Zhenhong Mai, Shufan Cui, Junmin Zhou, and Aiju Ding Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China

(Received 14 March 1989; accepted for publication 27 July 1989)

The stresses in GaAs/Si samples which were prepared under different growing conditions were determined by the x-ray diffraction method. The results show that the stress in GaAs/Si samples is reduced by improving the homogeneity of the thermal field. As the thickness ofthe epitaxial film increases, the curvature of the sample increases, but the stress remains in the same order.

I. INTRODUCTION

The growth of high-quality GaAs on Si substrate has been attracting increasing interest in recent years. Actually, the GaAs/Si structure has already been used to produce de­vices, 1-6 for example, high-quality modulation-doped field­effect transistors, light-emitting diodes, and so on. There is a strong tendency to prepare the III-V compound films on the 8i substrate because the III-V compounds possess optical, electrical, and high-frequency properties while 8i can be largely integrated. Nevertheless, there are still many proper­ties and structures of GaAs/Si which remain unknown.

One of the essential problems in GaAs/Si is the stress introduced during its growth. There are two main problems which strongly affect the quality of GaAs/Si. One is the large difference of the lattice constants between GaAs and Si, being about 4.1 %, the other is the large difference of their thermal expansion coefficients, which are 6.86 and 2.33 X 10-6 K - I for GaAs and Si, respectively. Additional­ly, the stress in GaAs/Si samples also depends on the grow­ing processes such as the growth temperature and the growth rate, the thickness of film, the quality and thickness of the substrate, the homogeneity of thermal field, and so on. Therefore, accurately determining the stress in GaAs/Si samples is important to improve growth conditions and the quality of this material.

X-RAY

~ FIG. i. Geometry of experiment.

II. EXPERIMENTS

The stress in GaAs/Si is determined by the x-ray dif­fraction method measuring the variance of the curvature of the samples. The principle of the method is shown in Fig. 1 where Ax is the translating direction which is along the di­rection of the diffraction vector and b.s is the moving dis­tance of a single step (2.5 cm is used in experiments). On is the Bragg angle at point n which represents that the sample is translated n step aiong the diameter from one edge of the sample. The radius of curvature between points nand n + 1 is given by

R=iJ.S/(e,,+l -0,,). (1)

Then the stress is given by

E T; 1 0'= -,

6(1-p) Tj R (2)

where E is the elastic modulus, p the Poisson's ratio, and T, and Tf are the thickness of substrate and film, respectively.

TABLE 1. Curvature and stress of difterent structures of samples. Note: The positive and the negative signs of the curvature mean that the film un­dergoes a tensile or compress stress, respectively.

Structure of Average radius Average No. Samples of curvature stress

Original Si sample - 182.9 In

2 GaAs (0.6,um)/Si 26.7m 3.00X 109 dyn/cm2

3 GaAs (0.8 ,ltm)/Si 19.7 m 3.05 X 10" dyn/cm2

4 GaAs (2.0jtm)/Si 9.3m 2.60x 109 dYIl/cm2

5 GaAs (O.8jtm)/SLS/Si SLS: 40 peri~s of

7.65 X 109 dyn/cm2 !IlGaAs (51 A) and SAm GaAs (42 A)

4767 J. AppL Phys. 66 (10), 15 November 1989 0021-8979/89/224767-03$02.40 © 1989 American Institute of Physics 4767 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

129.24.51.181 On: Fri, 28 Nov 2014 08:36:22

Xl02

J 1 I 60'-1\ I 1\ II

40 f I \ II I \ II .. I I \ II ~ 20 VI I \ I'

'" \ ~ ;0: ~ 0 -'1<-"-, -\ ;V/ I:'

~ \ I I I, \ I I,

-20 V II, Ilfr

-40 \1 :1 II

-60 I: !i-

0 10 20 30 40

posmo¥ Of S4IfPLfS 'MM)

FIG. 2. Variance of curvature along the surfaces of samples 2 and 5. (0) sample 2; ( X ) sample 5.

The value of E/(l-f.t} is 1.805 X 1012 dyn/cm2 for Si ( 100)9.

The experiments were done on the Rigaku UR-200 ro­tating anode x-ray generator with a Marconi LC-lOO topo­graphic camera, MoKa 1 radiation. The translation distance and the angle rotated are controlled by a microcomputer. The samples with different film structures were prepared by the MBE method under different growth conditions. The Si substrates were cut 4° off (100) towards (110) and are 400 pm thick. (022) diffraction was used. The influence of the homogeneity of the thermal field and the epitaxial layer structure on the stress was investigated.

III. RESULTS AND DISCUSSION

A. Small heating area

The heating area is about 35% of the sample area. One can see from Table I that under the same growth conditions, as the thickness of the epitaxial film increases, the curvature of the sample increases but the average stress varies very

TABLE II. Curvature and stress of different structure of samples.

No.

6

7

8

9

4768

Structure of sample

GaAs (2.0,um)/Si

GaAs (3.0 p.m)/Si

GaAs (0.8 ,um}/SLS/GaAs (1 ,um)/Si SLS: 10 periods oflnGaAs (l00 A.) and GaAs (100 A.)

GaAs (0.8 ,um)/SLS/GaAs (l/tm)/Si SLS: 10 periods of AIGaAs (100 A) and GaAs (100 A)

J. Appl. Phys., Vol. 66, No. 10,15 November 1989

1 em

FIG. 3. X ·ray topograph of GaAs (O.6,urn) lSi sample. Si (022) diffraction.

slightly; for example, see samples 2, 3, and 4. Both the curva­ture and the stress of the sample increase when the superlat­tke layer was introduced. Figure 2 shows the variance of the curvature of samples from one edge to another along the diameter. It is obvious that the curvature varies strongly in the center and the margin of the sample, especially for the sample containing the SLS layer, because of the large tem­perature gradient in these regions. The x-ray topograph also reveals a lot of dislocations in the center and margin of the sample (Fig. 3).

B. Larger heating area

The heating area is about 70% of the sample area. The experimental results are listed in Table II. It is shown that as the thickness of the epitaxial film increases, the radius of curvature decreases and the average stress changes a little. The variance of curvatures along the diameter of samples is shown in Fig. 4. The x-ray topograph (Fig. 5) shows that the

Average radius of curvature

~ 35.3 m

~ 34.0m

- 23.1 m

Average stress

~ 6.82X 10" dyn/cm2

- 4.72X 108 dyn/cm2

~ 4.64X 10" dyn/cmz

-~ 1.04 X 109 dyn/cm2

Li eta/. 4768 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

129.24.51.181 On: Fri, 28 Nov 2014 08:36:22

X103r------------------.,

-too

4()

Pl)',ITICtV 01 .'\'IIII'US (114M'

FIG, 4. Variance of curvature along the surfaces of samples 7 and 9. (0) sample 7; (X) sample 9.

defects in the center region of the sample are greatly im­proved, Comparing the results between sman and large heat­ing areas, it is clear that after improving the homogeneity of the thermal field, the stress has reduced 5-6 times and the oscillation of curvature along the samples is obviously im­proved. Moreover, the homogeneity of the thermal field strongly affects the curvature of the samples which contain the SLS structure. For the stress type, as is well known, the lattice mismatch between GaAs and Si makes a negative stress on the tUm while the difference of their thermal expan­sion induces a positive one. The experiments show that as the homogeneity of the thermal field is improved, there is a ten­dency to induce a negative stress. Therefore, the lattice dif­ference is a more important factor under this condition.

One can see from the experimental results that the quali­ty of GaAs/Si material is dominated by the film structure and growth condition. To obtain good-quality GaAs/Si ma­terials, several preparation conditions such as the tempera­ture of the substrate, the homogeneity of the thermal field. and the growth procedure must be precisely controlled, Moreover, the film structure is also an important factor af­fecting the quality of materials. After improving the homo­geneity of the thermal field, the optical and electrical proper­ties have been greatly improved. For example, the photoluminescence intensity increases about 10 times.

IVo CONCLUSIONS

( 1) As the homogeneity of the thermal field 1S Im­

proved, the stress in the GaAs/Si material is reduced.

4769 J. Appl. Phys., Vol. 66, No. i 0, 15 November 1 S89

1cm

FIG, S. X-raytopograph ofGaAs (1.0,um)/Sisample. Si (022) diffraction.

Whether the stress type is tensile or compressive depends on the growth conditions and the film structure.

(2) Under the same growth condition, with the thick­ness of epitaxial film increases, the curvature of samples in­creases, but the average stress almost remains at the same order.

(3) The average stress increases when the SLS structure is used, especially when the homogeneity of thermal field is worse.

'R, Fisher, T. Henderson, J, Clem, W. T. Masselink, W. Kopp, and H. Mor­ko", Electron Lett. 20. 945 (1984).

1R. Fisher, W. T. Masselink, J, K!em, T. Henderson, T. C. McGlinn, M, V. KHn, and H, Morko,<, J. App!. Phys. 58, 374 (1985),

3H. K. Choi, B-Y. Tsaur, G. M. Metze, G. W. Turner, and J. C. C. Fan, IEEE Electron Device Lett. EDL-6, 381 (1985).

40. M, Metze, H. K. Choi, and B-Y. Tsaur, App\. Phys, Leu. 45, 1107 (1984).

'Yo Shinod, T. Nishioka, and Y. Ohmachi, Jpn. J. Appl. Phys. 22, U50 (1983).

6R. Fisher. N. Chand, W. Kopp, H. Morkol!, L. P. Erickson, andR. Young· man, Appi. Phys. Lett. 47,397 (1985),

70e Peiwen and Mai Zhenhong, in Proceedings o/the International Con/er­ence on Materials and Process Characterization/or VLSI. edited by X-F. Zong, X-Yo Wang, and J. Chell (World Scientific, Singapore, 1988), p, 251.

8e. L. Kuo, P. E. Vanier, and J. C. Bilello, J. Appl. Phys. 55, 375 (1984). 9W. A. Brontley, J. Appl. Phys. 44,534 (1973).

Li at a/. 4769 [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP:

129.24.51.181 On: Fri, 28 Nov 2014 08:36:22