Stockholders' Equity (Details) - USD ($)	1 Months Ended	3 Months Ended				6 Months Ended		12 Months Ended	72 Months Ended
	Aug. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2015	Dec. 31, 2021	Oct. 27, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		$ 236,551,000	$ 229,846,000	$ 210,462,000	$ 207,969,000	$ 229,846,000	$ 207,969,000
Common stock options exercised		146,000		420,000	704,000
Investment in subsidiary with noncontrolling interest			(206,000)		(3,730,000)
Investment in subsidiary with noncontrolling interest	$ 334,000	1,179,000		575,000	576,000
Noncontrolling interest portion of Tongmei stock-based compensation		16,000	10,000
Stock-based compensation		919,000	875,000	975,000	816,000
Tongmei stock-based compensation		218,000	213,000
Transfer of subsidiary with redeemable noncontrolling interest				(1,241,000)
Sale of common stock to employees in connection with the reorganization					538,000
Investment in subsidiary from noncontrolling interest			1,887,000
Net income (loss)		5,996,000	3,554,000	4,479,000	3,736,000
Other comprehensive income (loss)		(6,561,000)	372,000	1,592,000	(147,000)
Balance, end of period		238,464,000	236,551,000	217,262,000	210,462,000	238,464,000	217,262,000		$ 229,846,000
Reclassification adjustment from AOCI		0		0		0	0
Net income attributable to redeemable noncontrolling interests		549,000				967,000
Other comprehensive income attributable to redeemable noncontrolling interests		$ 575,000				$ 529,000
Stock repurchase program, authorized amount										$ 5,000,000.0
Shares repurchased (in shares)		0				0		908,000	0
Average price of shares repurchased (in dollars per share)								$ 2.52
Total purchase price								$ 2,300,000
Stock repurchase program remaining authorized repurchase amount		$ 2,700,000				$ 2,700,000
Preferred Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000
Balance, end of period		3,532,000	3,532,000	3,532,000	3,532,000	3,532,000	3,532,000		$ 3,532,000
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		43,000	43,000	42,000	42,000	43,000	42,000
Balance, end of period		43,000	43,000	42,000	42,000	43,000	42,000		43,000
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		232,317,000	231,622,000	229,617,000	230,381,000	231,622,000	230,381,000
Common stock options exercised		146,000		420,000	704,000
Investment in subsidiary with noncontrolling interest			(410,000)		(2,691,000)
Investment in subsidiary with noncontrolling interest		(268,000)		(131,000)	(131,000)
Noncontrolling interest portion of Tongmei stock-based compensation		32,000	17,000
Stock-based compensation		919,000	875,000	975,000	816,000
Tongmei stock-based compensation		218,000	213,000
Transfer of subsidiary with noncontrolling interest				(1,229,000)
Transfer of subsidiary with redeemable noncontrolling interest				(1,241,000)
Sale of common stock to employees in connection with the reorganization					538,000
Balance, end of period		233,364,000	232,317,000	228,411,000	229,617,000	233,364,000	228,411,000		231,622,000
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		(26,805,000)	(29,970,000)	(41,120,000)	(44,545,000)	(29,970,000)	(44,545,000)
Net income (loss)		5,546,000	3,165,000	4,385,000	3,425,000
Balance, end of period		(21,259,000)	(26,805,000)	(36,735,000)	(41,120,000)	(21,259,000)	(36,735,000)		(29,970,000)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		6,629,000	6,302,000	3,078,000	3,209,000	6,302,000	3,209,000
Other comprehensive income (loss)		(5,992,000)	327,000	1,455,000	(131,000)
Balance, end of period		637,000	6,629,000	4,533,000	3,078,000	637,000	4,533,000		6,302,000
AXT, Inc. Stockholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		215,716,000	211,529,000	195,149,000	192,619,000	211,529,000	192,619,000
Common stock options exercised		146,000		420,000	704,000
Investment in subsidiary with noncontrolling interest			(410,000)		(2,691,000)
Investment in subsidiary with noncontrolling interest		(268,000)		(131,000)	(131,000)
Noncontrolling interest portion of Tongmei stock-based compensation		32,000	17,000
Stock-based compensation		919,000	875,000	975,000	816,000
Tongmei stock-based compensation		218,000	213,000
Transfer of subsidiary with noncontrolling interest				(1,229,000)
Transfer of subsidiary with redeemable noncontrolling interest				(1,241,000)
Sale of common stock to employees in connection with the reorganization					538,000
Net income (loss)		5,546,000	3,165,000	4,385,000	3,425,000
Other comprehensive income (loss)		(5,992,000)	327,000	1,455,000	(131,000)
Balance, end of period		216,317,000	215,716,000	199,783,000	195,149,000	216,317,000	199,783,000		211,529,000
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period		20,835,000	18,317,000	15,313,000	15,350,000	18,317,000	15,350,000
Investment in subsidiary with noncontrolling interest			204,000		(1,039,000)
Investment in subsidiary with noncontrolling interest		1,447,000		706,000	707,000
Noncontrolling interest portion of Tongmei stock-based compensation		(16,000)	(7,000)
Transfer of subsidiary with noncontrolling interest				1,229,000
Investment in subsidiary from noncontrolling interest			1,887,000
Net income (loss)		450,000	389,000	94,000	311,000
Other comprehensive income (loss)		(569,000)	45,000	137,000	(16,000)
Balance, end of period		$ 22,147,000	$ 20,835,000	$ 17,479,000	$ 15,313,000	$ 22,147,000	$ 17,479,000		$ 18,317,000