Business Segments - Schedule of Business Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net revenues	$ 20,174	$ 21,003	$ 20,633	$ 23,225	$ 23,079	$ 28,743	$ 21,115	$ 27,116	$ 85,035	$ 100,053	$ 83,073
Operating income (loss)	1,653	$ 1,351	$ 1,248	$ 664	(1,100)	$ 2,826	$ 1,485	$ 2,861	4,916	6,072	3,641
Capital expenditures									714	1,495	1,256
Depreciation and amortization									1,690	1,854	2,493
Identifiable assets	126,477				149,406				126,477	149,406
Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									583	994	418
Depreciation and amortization									1,125	1,053	1,373
Discontinued Operations
Segment Reporting Information [Line Items]
Identifiable assets	22,755				45,322				22,755	45,322
Operating Segments | Semiconductor
Segment Reporting Information [Line Items]
Net revenues									66,455	80,163	67,237
Operating income (loss)									8,744	11,848	9,538
Identifiable assets	56,855				59,744				56,855	59,744
Operating Segments | Semiconductor | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									379	352	236
Depreciation and amortization									828	715	876
Operating Segments | SiC/LED
Segment Reporting Information [Line Items]
Net revenues									13,682	13,761	10,248
Operating income (loss)									3,641	3,672	2,617
Identifiable assets	7,779				6,545				7,779	6,545
Operating Segments | SiC/LED | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									171	603	12
Depreciation and amortization									136	136	73
Operating Segments | Automation
Segment Reporting Information [Line Items]
Net revenues									4,898	6,129	5,588
Operating income (loss)									(786)	(2,897)	(724)
Identifiable assets	2,661				3,586				2,661	3,586
Operating Segments | Automation | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									22	25	148
Depreciation and amortization									103	135	325
Non-Segment
Segment Reporting Information [Line Items]
Operating income (loss)									(6,683)	(6,551)	(7,790)
Identifiable assets	$ 36,427				$ 34,209				36,427	34,209
Non-Segment | Continuing Operations
Segment Reporting Information [Line Items]
Capital expenditures									11	14	22
Depreciation and amortization									$ 58	$ 67	$ 99