No backing type found for UI property type big string

I tried to create a custom order type attribute using the below payload but ended up with an error.

Did I make any mistakes with the payload, or am I missing any required properties?

API Endpoint: {{baseURL}}/ccadmin/v1/orderTypes/:id

Method: PUT

Payload:

{

    "properties": {

        "apx_POAttachments": {

            "internalOnly": false,

            "default": "null",

            "localizable": false,

            "id": "apx_POAttachments",

            "label": "Purchase Order Attachments",

            "type": "big string"

        }

    }

}

Response:

{

    "errorCode": "20196",

    "message": "No backing type found for UI property type big string",

    "status": "500"

}