Balance Sheet Components - Intangible assets (Details) - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 19,455,000	$ 19,455,000
Less accumulated amortization	(2,954,000)	(2,842,000)
Intangible Assets, Net (Excluding Goodwill)	16,501,000	16,613,000
Goodwill	269,000	269,000
Intangible assets, net	16,770,000	16,882,000
Amortization expense	113,000	113,000	$ 76,000
Patents and exclusive technology rights [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	18,037,000	18,037,000
Trade name [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	268,000	268,000
Customer relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	1,150,000	$ 1,150,000
STMicro [Member] | Licensing Agreements [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 16,200,000