Business Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Segment Reporting Information [Line Items]
Number of business segments | segment			3
Net revenues	$ 21,003	$ 28,743	$ 64,861	$ 76,974
Operating income (loss)	1,351	2,826	3,263	7,172
Identifiable assets	127,426		127,426		$ 149,406
Operating Segments | Semiconductor
Segment Reporting Information [Line Items]
Net revenues	16,254	23,472	51,267	60,945
Operating income (loss)	1,951	3,861	6,428	9,122
Identifiable assets	60,086		60,086		59,744
Operating Segments | SiC/LED
Segment Reporting Information [Line Items]
Net revenues	3,074	3,594	9,330	10,720
Operating income (loss)	607	938	2,253	3,153
Identifiable assets	7,635		7,635		6,545
Operating Segments | Automation
Segment Reporting Information [Line Items]
Net revenues	1,675	1,677	4,264	5,309
Operating income (loss)	(52)	(195)	(392)	(231)
Identifiable assets	2,753		2,753		3,586
Non-Segment
Segment Reporting Information [Line Items]
Operating income (loss)	(1,155)	$ (1,778)	(5,026)	$ (4,872)
Identifiable assets	33,987		33,987		34,209
Discontinued Operations
Segment Reporting Information [Line Items]
Identifiable assets	$ 22,965		$ 22,965		$ 45,322