Temperature Field Control for the Growth of 150 mm Diameter CZT Crystals

doi:10.16553/j.cnki.issn1000-985x.2025.0217

Abstract

Abstract: Cadmium zinc telluride（CZT）is a crucial material in the fields of infrared detection and nuclear radiation detection， garnering significant attention as a foundational material for manufacturing next-generation ultra-large array detectors. To address the technical challenges in growing 150 mm diameter CZT crystals via the Vertical gradient freeze （VGF） method， finite element simulation was employed to regulate the heater output power during the crystal growth process. This approach enabled precise control over the temperature field during CZT crystal growth， achieving a convex solid-liquid interface shape throughout the entire growth process. Consequently， high-quality 150 mm diameter CZT single crystals were successfully grown. The grown crystals enabled the preparation of 100 mm×100 mm infrared CZT substrates. Test results demonstrate uniform composition distribution in the CZT crystals. The full width at half maximum （FWHM） of the rocking curve for the （111） plane of the CZT substrates is below 15″， and the average etch pit density （EPD） is less than 1×10⁴ cm^-2.

Key words: CdZnTe crystal; vertical gradient freeze method; finite element simulation; interface shape control; composition uniformity; crystal defect

CLC Number:

CAO Cong, LIU Jianggao, SHE Weilin, FAN Yexia, MA Qisi, LI Zhenxing. Temperature Field Control for the Growth of 150 mm Diameter CZT Crystals[J]. Journal of Synthetic Crystals, 2026, 55(3): 359-367.

Figures/Tables 14

Fig.1 Schematic diagram of the CdZnTe crystal growth system. （a） Finite element simulation model；（b） heat transfer at the crystal growth interface［17］

Table 1 Material properties used in simulation［13，15?16］

Material	State	Thermal conductivity/（W·m^-1·K^-1）	Heat capacity /（J·kg^-1·K^-1）	Density/（kg·m^-3）	Emissivity	Comment
CZT	Solid	0.9	159	5 850	0.7	Melting temperature 1 371 K
CZT	Liquid	1.0	187	5 740	0.7	Latent heat 209 kJ/kg
Quartz	Solid	1.4	1 232	2 650	0.9
pBN	Solid	63（a），25（c）	1 580	1 950	0.5
Kanthal-alloy	Solid	15	720	7 100	0.7
Corundum	Solid	15	920	3 540	0.86
SiC	Solid	120	650	3 170	0.8
Cera-fiber	Solid	0.39	1 130	210	0.5
Air	Liquid	0.03	1 009	Ideal gas law	—
Cd vapor	Liquid	0.02	106	0.33	—

Fig.2 Schematic diagram of crystal growth simulation at the initial stage

Fig.3 Schematic diagram of the simulation at different stages of crystal growth （power reduction ratio is 2∶3∶4）. （a） Transition stage；（b） constant diameter growth stage；（c） end of crystal growth stage

Fig.4 Schematic diagram of the simulation at different stages of crystal growth （power reduction ratio is 2∶4∶5）. （a） Transition stage；（b） constant diameter growth stage；（c） end of crystal growth stage

Fig.5 Schematic diagram of the simulation at different stages of crystal growth （power reduction ratio is 2∶5∶6）. （a） Transition stage；（b） constant diameter growth stage；（c） end of crystal growth stage

Fig.6 Schematic diagram of crystal growth rate control in transient simulation

Table 2 PID parameter control statistics of CdZnTe crystal growth system

Sample	PID	Power fluctuation range， ΔP/%	Temperature control deviation， ΔT/℃	Temperature fluctuation range， ΔT_f/℃
#1	P control	0.22	-4.66	0.14
#2	P and I control	0.26	-0.11	0.19
#3	P， I and D control	0.49	0.04	0.07
#4	Self-adaption	0.22	-0.08	0.14

Fig.7 Schematic diagram of output power fluctuations in temperature zones under different PID control parameters

Fig.8 Schematic diagram of furnace temperature fluctuation under different PID control parameters

Fig.9 CdZnTe crystal material. （a） Side view of the crystal；（b） view of the crystal tail end；（c） 100 mm×100 mm CdZnTe substrate

Fig.10 Crystal composition distribution uniformity test. （a） 150 mm diameter CdZnTe wafer；（b） PL spectrum；（c） Zn composition distribution spectrum

Fig.11 Half-width and dislocation test of CdZnTe substrate. （a）（111） B-plane diffraction peak；（b） substrate dislocation corrosion morphology

Table 3 Statistical results of FWHM and dislocation tests for 100 mm×100 mm CZT substrates

Sample	FWHM/（″）	Dislocation density/cm^-2
Point 1	11.16	6.00×10³
Point 2	9.09	4.58×10³
Point 3	13.57	6.52×10³
Point 4	8.73	4.06×10³
Point 5	8.31	5.82×10³
Average	10.17	5.40×10³

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